source: mainline/uspace/lib/fs/libfs.c@ 51774cd

/*
 * Copyright (c) 2009 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 libfs
 * @{
 */
/**
 * @file
 * Glue code which is common to all FS implementations.
 */

#include "libfs.h"
#include <macros.h>
#include <errno.h>
#include <async.h>
#include <as.h>
#include <assert.h>
#include <dirent.h>
#include <mem.h>
#include <str.h>
#include <stdlib.h>
#include <fibril_synch.h>
#include <ipc/vfs.h>
#include <vfs/vfs.h>

#define on_error(rc, action) \
        do { \
                if ((rc) != EOK) \
                        action; \
        } while (0)

#define combine_rc(rc1, rc2) \
        ((rc1) == EOK ? (rc2) : (rc1))

#define answer_and_return(rid, rc) \
        do { \
                async_answer_0((rid), (rc)); \
                return; \
        } while (0)

static fs_reg_t reg;

static vfs_out_ops_t *vfs_out_ops = NULL;
static libfs_ops_t *libfs_ops = NULL;

static char fs_name[FS_NAME_MAXLEN + 1];

static void libfs_link(libfs_ops_t *, fs_handle_t, ipc_callid_t,
    ipc_call_t *);
static void libfs_lookup(libfs_ops_t *, fs_handle_t, ipc_callid_t,
    ipc_call_t *);
static void libfs_stat(libfs_ops_t *, fs_handle_t, ipc_callid_t, ipc_call_t *);
static void libfs_open_node(libfs_ops_t *, fs_handle_t, ipc_callid_t,
    ipc_call_t *);
static void libfs_statfs(libfs_ops_t *, fs_handle_t, ipc_callid_t,
    ipc_call_t *);

static void vfs_out_mounted(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        char *opts;
        int rc;
        
        /* Accept the mount options. */
        rc = async_data_write_accept((void **) &opts, true, 0, 0, 0, NULL);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                return;
        }

        fs_index_t index;
        aoff64_t size;
        unsigned lnkcnt;
        rc = vfs_out_ops->mounted(service_id, opts, &index, &size, &lnkcnt);

        if (rc == EOK)
                async_answer_4(rid, EOK, index, LOWER32(size), UPPER32(size),
                    lnkcnt);
        else
                async_answer_0(rid, rc);

        free(opts);
}

static void vfs_out_unmounted(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        int rc; 

        rc = vfs_out_ops->unmounted(service_id);

        async_answer_0(rid, rc);
}

static void vfs_out_link(ipc_callid_t rid, ipc_call_t *req)
{
        libfs_link(libfs_ops, reg.fs_handle, rid, req);
}

static void vfs_out_lookup(ipc_callid_t rid, ipc_call_t *req)
{
        libfs_lookup(libfs_ops, reg.fs_handle, rid, req);
}

static void vfs_out_read(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        aoff64_t pos = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*req),
            IPC_GET_ARG4(*req));
        size_t rbytes;
        int rc;

        rc = vfs_out_ops->read(service_id, index, pos, &rbytes);

        if (rc == EOK)
                async_answer_1(rid, EOK, rbytes);
        else
                async_answer_0(rid, rc);
}

static void vfs_out_write(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        aoff64_t pos = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*req),
            IPC_GET_ARG4(*req));
        size_t wbytes;
        aoff64_t nsize;
        int rc;

        rc = vfs_out_ops->write(service_id, index, pos, &wbytes, &nsize);

        if (rc == EOK) {
                async_answer_3(rid, EOK, wbytes, LOWER32(nsize),
                    UPPER32(nsize));
        } else
                async_answer_0(rid, rc);
}

static void vfs_out_truncate(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        aoff64_t size = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*req),
            IPC_GET_ARG4(*req));
        int rc;

        rc = vfs_out_ops->truncate(service_id, index, size);

        async_answer_0(rid, rc);
}

static void vfs_out_close(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        int rc;

        rc = vfs_out_ops->close(service_id, index);

        async_answer_0(rid, rc);
}

static void vfs_out_destroy(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);

        int rc;
        fs_node_t *node = NULL;
        rc = libfs_ops->node_get(&node, service_id, index);
        if (rc == EOK && node != NULL) {
                bool destroy = (libfs_ops->lnkcnt_get(node) == 0);
                libfs_ops->node_put(node);
                if (destroy)
                        rc = vfs_out_ops->destroy(service_id, index);
        }
        async_answer_0(rid, rc);
}

static void vfs_out_open_node(ipc_callid_t rid, ipc_call_t *req)
{
        libfs_open_node(libfs_ops, reg.fs_handle, rid, req);
}

static void vfs_out_stat(ipc_callid_t rid, ipc_call_t *req)
{
        libfs_stat(libfs_ops, reg.fs_handle, rid, req);
}

static void vfs_out_sync(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        int rc;

        rc = vfs_out_ops->sync(service_id, index);

        async_answer_0(rid, rc);
}

static void vfs_out_statfs(ipc_callid_t rid, ipc_call_t *req)
{
        libfs_statfs(libfs_ops, reg.fs_handle, rid, req);
}

static void vfs_out_is_empty(ipc_callid_t rid, ipc_call_t *req)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*req);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*req);
        int rc;

        fs_node_t *node = NULL;
        rc = libfs_ops->node_get(&node, service_id, index);
        if (rc != EOK)
                async_answer_0(rid, rc);
        if (node == NULL)
                async_answer_0(rid, EINVAL);
        
        bool children = false;
        rc = libfs_ops->has_children(&children, node);
        libfs_ops->node_put(node);
        
        if (rc != EOK)
                async_answer_0(rid, rc);
        async_answer_0(rid, children ? ENOTEMPTY : EOK);
}

static void vfs_connection(ipc_callid_t iid, ipc_call_t *icall, void *arg)
{
        if (iid) {
                /*
                 * This only happens for connections opened by
                 * IPC_M_CONNECT_ME_TO calls as opposed to callback connections
                 * created by IPC_M_CONNECT_TO_ME.
                 */
                async_answer_0(iid, EOK);
        }
        
        while (true) {
                ipc_call_t call;
                ipc_callid_t callid = async_get_call(&call);
                
                if (!IPC_GET_IMETHOD(call))
                        return;
                
                switch (IPC_GET_IMETHOD(call)) {
                case VFS_OUT_MOUNTED:
                        vfs_out_mounted(callid, &call);
                        break;
                case VFS_OUT_UNMOUNTED:
                        vfs_out_unmounted(callid, &call);
                        break;
                case VFS_OUT_LINK:
                        vfs_out_link(callid, &call);
                        break;
                case VFS_OUT_LOOKUP:
                        vfs_out_lookup(callid, &call);
                        break;
                case VFS_OUT_READ:
                        vfs_out_read(callid, &call);
                        break;
                case VFS_OUT_WRITE:
                        vfs_out_write(callid, &call);
                        break;
                case VFS_OUT_TRUNCATE:
                        vfs_out_truncate(callid, &call);
                        break;
                case VFS_OUT_CLOSE:
                        vfs_out_close(callid, &call);
                        break;
                case VFS_OUT_DESTROY:
                        vfs_out_destroy(callid, &call);
                        break;
                case VFS_OUT_OPEN_NODE:
                        vfs_out_open_node(callid, &call);
                        break;
                case VFS_OUT_STAT:
                        vfs_out_stat(callid, &call);
                        break;
                case VFS_OUT_SYNC:
                        vfs_out_sync(callid, &call);
                        break;
                case VFS_OUT_STATFS:
                        vfs_out_statfs(callid, &call);
                        break;
                case VFS_OUT_IS_EMPTY:
                        vfs_out_is_empty(callid, &call);
                        break;
                default:
                        async_answer_0(callid, ENOTSUP);
                        break;
                }
        }
}

/** Register file system server.
 *
 * This function abstracts away the tedious registration protocol from
 * file system implementations and lets them to reuse this registration glue
 * code.
 *
 * @param sess Session for communication with VFS.
 * @param info VFS info structure supplied by the file system
 *             implementation.
 * @param vops Address of the vfs_out_ops_t structure.
 * @param lops Address of the libfs_ops_t structure.
 *
 * @return EOK on success or a non-zero error code on errror.
 *
 */
int fs_register(async_sess_t *sess, vfs_info_t *info, vfs_out_ops_t *vops,
    libfs_ops_t *lops)
{
        /*
         * Tell VFS that we are here and want to get registered.
         * We use the async framework because VFS will answer the request
         * out-of-order, when it knows that the operation succeeded or failed.
         */
        
        async_exch_t *exch = async_exchange_begin(sess);
        
        ipc_call_t answer;
        aid_t req = async_send_0(exch, VFS_IN_REGISTER, &answer);
        
        /*
         * Send our VFS info structure to VFS.
         */
        int rc = async_data_write_start(exch, info, sizeof(*info));
        
        if (rc != EOK) {
                async_exchange_end(exch);
                async_forget(req);
                return rc;
        }
        
        /*
         * Set VFS_OUT and libfs operations.
         */
        vfs_out_ops = vops;
        libfs_ops = lops;

        str_cpy(fs_name, sizeof(fs_name), info->name);

        /*
         * Ask VFS for callback connection.
         */
        port_id_t port;
        rc = async_create_callback_port(exch, INTERFACE_VFS_DRIVER_CB, 0, 0,
            vfs_connection, NULL, &port);
        
        /*
         * Request sharing the Path Lookup Buffer with VFS.
         */
        rc = async_share_in_start_0_0(exch, PLB_SIZE, (void *) &reg.plb_ro);
        if (reg.plb_ro == AS_MAP_FAILED) {
                async_exchange_end(exch);
                async_forget(req);
                return ENOMEM;
        }
        
        async_exchange_end(exch);
        
        if (rc) {
                async_forget(req);
                return rc;
        }
         
        /*
         * Pick up the answer for the request to the VFS_IN_REQUEST call.
         */
        async_wait_for(req, NULL);
        reg.fs_handle = (int) IPC_GET_ARG1(answer);
        
        /*
         * Tell the async framework that other connections are to be handled by
         * the same connection fibril as well.
         */
        async_set_fallback_port_handler(vfs_connection, NULL);
        
        return IPC_GET_RETVAL(answer);
}

void fs_node_initialize(fs_node_t *fn)
{
        memset(fn, 0, sizeof(fs_node_t));
}

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

static int plb_get_component(char *dest, unsigned *sz, unsigned *ppos,
    unsigned last)
{
        unsigned pos = *ppos;
        unsigned size = 0;
        
        if (pos == last) {
                *sz = 0;
                return ERANGE;
        }

        char c = plb_get_char(pos); 
        if (c == '/')
                pos++;
        
        for (int i = 0; i <= NAME_MAX; i++) {
                c = plb_get_char(pos);
                if (pos == last || c == '/') {
                        dest[i] = 0;
                        *ppos = pos;
                        *sz = size;
                        return EOK;
                }
                dest[i] = c;
                pos++;
                size++;
        }
        return ENAMETOOLONG;
}

static int receive_fname(char *buffer)
{
        size_t size;
        ipc_callid_t wcall;
        
        if (!async_data_write_receive(&wcall, &size))
                return ENOENT;
        if (size > NAME_MAX + 1) {
                async_answer_0(wcall, ERANGE);
                return ERANGE;
        }
        return async_data_write_finalize(wcall, buffer, size);
}

/** Link a file at a path.
 */
void libfs_link(libfs_ops_t *ops, fs_handle_t fs_handle, ipc_callid_t rid,
    ipc_call_t *req)
{
        service_id_t parent_sid = IPC_GET_ARG1(*req);
        fs_index_t parent_index = IPC_GET_ARG2(*req);
        fs_index_t child_index = IPC_GET_ARG3(*req);
        
        char component[NAME_MAX + 1];
        int rc = receive_fname(component);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                return;
        }

        fs_node_t *parent = NULL;
        rc = ops->node_get(&parent, parent_sid, parent_index);
        if (parent == NULL) {
                async_answer_0(rid, rc == EOK ? EBADF : rc);
                return;
        }
        
        fs_node_t *child = NULL;
        rc = ops->node_get(&child, parent_sid, child_index);
        if (child == NULL) {
                async_answer_0(rid, rc == EOK ? EBADF : rc);
                ops->node_put(parent);
                return;
        }
        
        rc = ops->link(parent, child, component);
        ops->node_put(parent);
        ops->node_put(child);
        async_answer_0(rid, rc);
}

/** Lookup VFS triplet by name in the file system name space.
 *
 * The path passed in the PLB must be in the canonical file system path format
 * as returned by the canonify() function.
 *
 * @param ops       libfs operations structure with function pointers to
 *                  file system implementation
 * @param fs_handle File system handle of the file system where to perform
 *                  the lookup.
 * @param rid       Request ID of the VFS_OUT_LOOKUP request.
 * @param request   VFS_OUT_LOOKUP request data itself.
 *
 */
void libfs_lookup(libfs_ops_t *ops, fs_handle_t fs_handle, ipc_callid_t rid,
    ipc_call_t *req)
{
        unsigned first = IPC_GET_ARG1(*req);
        unsigned len = IPC_GET_ARG2(*req);
        service_id_t service_id = IPC_GET_ARG3(*req);
        fs_index_t index = IPC_GET_ARG4(*req);
        int lflag = IPC_GET_ARG5(*req);
        
        assert((int) index != -1);
        
        // TODO: Validate flags.
        
        unsigned next = first;
        unsigned last = first + len;
        
        char component[NAME_MAX + 1];
        int rc;
        
        fs_node_t *par = NULL;
        fs_node_t *cur = NULL;
        fs_node_t *tmp = NULL;
        unsigned clen = 0;
        
        rc = ops->node_get(&cur, service_id, index);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                goto out;
        }
        
        assert(cur != NULL);
        
        /* Find the file and its parent. */
        
        unsigned last_next = 0;
        
        while (next != last) {
                if (cur == NULL) {
                        assert(par != NULL);
                        goto out1;
                }

                if (!ops->is_directory(cur)) {
                        async_answer_0(rid, ENOTDIR);
                        goto out;
                }
                
                last_next = next;
                /* Collect the component */
                rc = plb_get_component(component, &clen, &next, last);
                assert(rc != ERANGE);
                if (rc != EOK) {
                        async_answer_0(rid, rc);
                        goto out;
                }
                
                if (clen == 0) {
                        /* The path is just "/". */
                        break;
                }
                
                assert(component[clen] == 0);
                
                /* Match the component */
                rc = ops->match(&tmp, cur, component);
                if (rc != EOK) {
                        async_answer_0(rid, rc);
                        goto out;
                }
                
                /* Descend one level */
                if (par) {
                        rc = ops->node_put(par);
                        if (rc != EOK) {
                                async_answer_0(rid, rc);
                                goto out;
                        }
                }
                
                par = cur;
                cur = tmp;
                tmp = NULL;
        }
        
        /* At this point, par is either NULL or a directory.
         * If cur is NULL, the looked up file does not exist yet.
         */
         
        assert(par == NULL || ops->is_directory(par));
        assert(par != NULL || cur != NULL);
        
        /* Check for some error conditions. */
        
        if (cur && (lflag & L_FILE) && (ops->is_directory(cur))) {
                async_answer_0(rid, EISDIR);
                goto out;
        }
        
        if (cur && (lflag & L_DIRECTORY) && (ops->is_file(cur))) {
                async_answer_0(rid, ENOTDIR);
                goto out;
        }
        
        /* Unlink. */
        
        if (lflag & L_UNLINK) {
                if (!cur) {
                        async_answer_0(rid, ENOENT);
                        goto out;
                }
                if (!par) {
                        async_answer_0(rid, EINVAL);
                        goto out;
                }
                
                rc = ops->unlink(par, cur, component);
                if (rc == EOK) {
                        aoff64_t size = ops->size_get(cur);
                        async_answer_5(rid, fs_handle, service_id,
                            ops->index_get(cur),
                            (ops->is_directory(cur) << 16) | last,
                            LOWER32(size), UPPER32(size));
                } else {
                        async_answer_0(rid, rc);
                }
                goto out;
        }
        
        /* Create. */
        
        if (lflag & L_CREATE) {
                if (cur && (lflag & L_EXCLUSIVE)) {
                        async_answer_0(rid, EEXIST);
                        goto out;
                }
        
                if (!cur) {
                        rc = ops->create(&cur, service_id,
                            lflag & (L_FILE | L_DIRECTORY));
                        if (rc != EOK) {
                                async_answer_0(rid, rc);
                                goto out;
                        }
                        if (!cur) {
                                async_answer_0(rid, ENOSPC);
                                goto out;
                        }
                        
                        rc = ops->link(par, cur, component);
                        if (rc != EOK) {
                                (void) ops->destroy(cur);
                                cur = NULL;
                                async_answer_0(rid, rc);
                                goto out;
                        }
                }
        }
        
        /* Return. */
out1:
        if (!cur) {
                async_answer_5(rid, fs_handle, service_id, ops->index_get(par),
                    last_next, -1, true);
                goto out;
        }
        
        aoff64_t size = ops->size_get(cur);
        async_answer_5(rid, fs_handle, service_id, ops->index_get(cur),
            (ops->is_directory(cur) << 16) | last, LOWER32(size),
            UPPER32(size));
        
out:
        if (par)
                (void) ops->node_put(par);
        
        if (cur)
                (void) ops->node_put(cur);
        
        if (tmp)
                (void) ops->node_put(tmp);
}

void libfs_stat(libfs_ops_t *ops, fs_handle_t fs_handle, ipc_callid_t rid,
    ipc_call_t *request)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);

        fs_node_t *fn;
        int rc = ops->node_get(&fn, service_id, index);
        on_error(rc, answer_and_return(rid, rc));

        ipc_callid_t callid;
        size_t size;
        if ((!async_data_read_receive(&callid, &size)) ||
            (size != sizeof(struct stat))) {
                ops->node_put(fn);
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }

        struct stat stat;
        memset(&stat, 0, sizeof(struct stat));

        stat.fs_handle = fs_handle;
        stat.service_id = service_id;
        stat.index = index;
        stat.lnkcnt = ops->lnkcnt_get(fn);
        stat.is_file = ops->is_file(fn);
        stat.is_directory = ops->is_directory(fn);
        stat.size = ops->size_get(fn);
        stat.service = ops->service_get(fn);

        ops->node_put(fn);


        async_data_read_finalize(callid, &stat, sizeof(struct stat));
        async_answer_0(rid, EOK);
}

void libfs_statfs(libfs_ops_t *ops, fs_handle_t fs_handle, ipc_callid_t rid,
    ipc_call_t *request)
{
        service_id_t service_id = (service_id_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);

        fs_node_t *fn;
        int rc = ops->node_get(&fn, service_id, index);
        on_error(rc, answer_and_return(rid, rc));

        ipc_callid_t callid;
        size_t size;
        if ((!async_data_read_receive(&callid, &size)) ||
            (size != sizeof(struct statfs))) {
                goto error;
        }

        struct statfs st;
        memset(&st, 0, sizeof(struct statfs));

        str_cpy(st.fs_name, sizeof(st.fs_name), fs_name);

        if (ops->size_block != NULL) {
                rc = ops->size_block(service_id, &st.f_bsize);
                if (rc != EOK)
                        goto error;
        }

        if (ops->total_block_count != NULL) {
                rc = ops->total_block_count(service_id, &st.f_blocks);
                if (rc != EOK)
                        goto error;
        }

        if (ops->free_block_count != NULL) {
                rc = ops->free_block_count(service_id, &st.f_bfree);
                if (rc != EOK)
                        goto error;
        }

        ops->node_put(fn);
        async_data_read_finalize(callid, &st, sizeof(struct statfs));
        async_answer_0(rid, EOK);
        return;

error:
        ops->node_put(fn);
        async_answer_0(callid, EINVAL);
        async_answer_0(rid, EINVAL);
}


/** Open VFS triplet.
 *
 * @param ops     libfs operations structure with function pointers to
 *                file system implementation
 * @param rid     Request ID of the VFS_OUT_OPEN_NODE request.
 * @param request VFS_OUT_OPEN_NODE request data itself.
 *
 */
void libfs_open_node(libfs_ops_t *ops, fs_handle_t fs_handle, ipc_callid_t rid,
    ipc_call_t *request)
{
        service_id_t service_id = IPC_GET_ARG1(*request);
        fs_index_t index = IPC_GET_ARG2(*request);
        
        fs_node_t *fn;
        int rc = ops->node_get(&fn, service_id, index);
        on_error(rc, answer_and_return(rid, rc));
        
        if (fn == NULL) {
                async_answer_0(rid, ENOENT);
                return;
        }
        
        rc = ops->node_open(fn);
        aoff64_t size = ops->size_get(fn);
        async_answer_4(rid, rc, LOWER32(size), UPPER32(size),
            ops->lnkcnt_get(fn),
            (ops->is_file(fn) ? L_FILE : 0) |
            (ops->is_directory(fn) ? L_DIRECTORY : 0));
        
        (void) ops->node_put(fn);
}

static FIBRIL_MUTEX_INITIALIZE(instances_mutex);
static LIST_INITIALIZE(instances_list);

typedef struct {
        service_id_t service_id;
        link_t link;
        void *data;
} fs_instance_t;

int fs_instance_create(service_id_t service_id, void *data)
{
        fs_instance_t *inst = malloc(sizeof(fs_instance_t));
        if (!inst)
                return ENOMEM;

        link_initialize(&inst->link);
        inst->service_id = service_id;
        inst->data = data;

        fibril_mutex_lock(&instances_mutex);
        list_foreach(instances_list, link, fs_instance_t, cur) {
                if (cur->service_id == service_id) {
                        fibril_mutex_unlock(&instances_mutex);
                        free(inst);
                        return EEXIST;
                }

                /* keep the list sorted */
                if (cur->service_id < service_id) {
                        list_insert_before(&inst->link, &cur->link);
                        fibril_mutex_unlock(&instances_mutex);
                        return EOK;
                }
        }
        list_append(&inst->link, &instances_list);
        fibril_mutex_unlock(&instances_mutex);

        return EOK;
}

int fs_instance_get(service_id_t service_id, void **idp)
{
        fibril_mutex_lock(&instances_mutex);
        list_foreach(instances_list, link, fs_instance_t, inst) {
                if (inst->service_id == service_id) {
                        *idp = inst->data;
                        fibril_mutex_unlock(&instances_mutex);
                        return EOK;
                }
        }
        fibril_mutex_unlock(&instances_mutex);
        return ENOENT;
}

int fs_instance_destroy(service_id_t service_id)
{
        fibril_mutex_lock(&instances_mutex);
        list_foreach(instances_list, link, fs_instance_t, inst) {
                if (inst->service_id == service_id) {
                        list_remove(&inst->link);
                        fibril_mutex_unlock(&instances_mutex);
                        free(inst);
                        return EOK;
                }
        }
        fibril_mutex_unlock(&instances_mutex);
        return ENOENT;
}

/** @}
 */