source: mainline/uspace/srv/vfs/vfs_ops.c@ 5126f80

/*
 * 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 vfs_ops.c
 * @brief Operations that VFS offers to its clients.
 */

#include "vfs.h"
#include <macros.h>
#include <stdint.h>
#include <async.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <str.h>
#include <stdbool.h>
#include <fibril_synch.h>
#include <adt/list.h>
#include <unistd.h>
#include <ctype.h>
#include <fcntl.h>
#include <assert.h>
#include <vfs/canonify.h>
#include <vfs/vfs_mtab.h>

FIBRIL_MUTEX_INITIALIZE(mtab_list_lock);
LIST_INITIALIZE(mtab_list);
static size_t mtab_size = 0;

/* Forward declarations of static functions. */
static int vfs_truncate_internal(fs_handle_t, service_id_t, fs_index_t,
    aoff64_t);

/**
 * This rwlock prevents the race between a triplet-to-VFS-node resolution and a
 * concurrent VFS operation which modifies the file system namespace.
 */
FIBRIL_RWLOCK_INITIALIZE(namespace_rwlock);

static int vfs_connect_internal(service_id_t service_id, unsigned flags, unsigned instance,
    char *options, char *fsname, vfs_node_t **root)
{
        fs_handle_t fs_handle = 0;
        
        fibril_mutex_lock(&fs_list_lock);
        while (1) {
                fs_handle = fs_name_to_handle(instance, fsname, false);
                
                if (fs_handle != 0 || !(flags & VFS_MOUNT_BLOCKING)) {
                        break;
                }
                
                fibril_condvar_wait(&fs_list_cv, &fs_list_lock);
        }
        fibril_mutex_unlock(&fs_list_lock);

        if (fs_handle == 0) {
                return ENOENT;
        }
        
        /* Tell the mountee that it is being mounted. */
        ipc_call_t answer;
        async_exch_t *exch = vfs_exchange_grab(fs_handle);
        aid_t msg = async_send_1(exch, VFS_OUT_MOUNTED, (sysarg_t) service_id, &answer);
        /* Send the mount options */
        sysarg_t rc = async_data_write_start(exch, options, str_size(options));
        if (rc != EOK) {
                async_forget(msg);
                vfs_exchange_release(exch);
                return rc;
        }
        async_wait_for(msg, &rc);
        vfs_exchange_release(exch);
        
        if (rc != EOK) {
                return rc;
        }
        
        vfs_lookup_res_t res;
        res.triplet.fs_handle = fs_handle;
        res.triplet.service_id = service_id;
        res.triplet.index = (fs_index_t) IPC_GET_ARG1(answer);
        res.size = (int64_t) MERGE_LOUP32(IPC_GET_ARG2(answer), IPC_GET_ARG3(answer));
        res.type = VFS_NODE_DIRECTORY;
        
        /* Add reference to the mounted root. */
        *root = vfs_node_get(&res); 
        assert(*root);
                        
        return EOK;
}

void vfs_mount_srv(ipc_callid_t rid, ipc_call_t *request)
{
        int mpfd = IPC_GET_ARG1(*request);
        
        /*
         * We expect the library to do the device-name to device-handle
         * translation for us, thus the device handle will arrive as ARG1
         * in the request.
         */
        service_id_t service_id = (service_id_t) IPC_GET_ARG2(*request);
        
        /*
         * Mount flags are passed as ARG2.
         */
        unsigned int flags = (unsigned int) IPC_GET_ARG3(*request);
        
        /*
         * Instance number is passed as ARG3.
         */
        unsigned int instance = IPC_GET_ARG4(*request);
        
        char *opts = NULL;
        char *fs_name = NULL;
        vfs_file_t *mp = NULL;
        vfs_file_t *file = NULL;
        int fd = -1;
        mtab_ent_t *mtab_ent = NULL;

        /* Now we expect to receive the mount options. */
        int rc = async_data_write_accept((void **) &opts, true, 0, MAX_MNTOPTS_LEN,
            0, NULL);
        if (rc != EOK) {
                async_data_write_void(rc);
                goto out;
        }
        
        /*
         * Now, we expect the client to send us data with the name of the file
         * system.
         */
        rc = async_data_write_accept((void **) &fs_name, true, 0,
            FS_NAME_MAXLEN, 0, NULL);
        if (rc != EOK) {
                goto out;
        }
        
        if (!(flags & VFS_MOUNT_CONNECT_ONLY)) {
                mp = vfs_file_get(mpfd);
                if (mp == NULL) {
                        rc = EBADF;
                        goto out;
                }
                
                if (mp->node->mount != NULL) {
                        rc = EBUSY;
                        goto out;
                }
                
                if (mp->node->type != VFS_NODE_DIRECTORY) {
                        rc = ENOTDIR;
                        goto out;
                }
                
                if (vfs_node_has_children(mp->node)) {
                        rc = ENOTEMPTY;
                        goto out;
                }
        }
        
        if (!(flags & VFS_MOUNT_NO_REF)) {
                fd = vfs_fd_alloc(&file, false);
                if (fd < 0) {
                        rc = fd;
                        goto out;
                }
        }
        
        /* Add the filesystem info to the list of mounted filesystems */
        mtab_ent = malloc(sizeof(mtab_ent_t));
        if (!mtab_ent) {
                rc = ENOMEM;
                goto out;
        }
        
        vfs_node_t *root = NULL;
        
        fibril_rwlock_write_lock(&namespace_rwlock);

        rc = vfs_connect_internal(service_id, flags, instance, opts, fs_name, &root);
        if (rc == EOK && !(flags & VFS_MOUNT_CONNECT_ONLY)) {
                vfs_node_addref(mp->node);
                vfs_node_addref(root);
                mp->node->mount = root;
        }
        
        fibril_rwlock_write_unlock(&namespace_rwlock);
        
        if (rc != EOK) {
                goto out;
        }
        
        
        if (flags & VFS_MOUNT_NO_REF) {
                vfs_node_delref(root);
        } else {
                assert(file != NULL);
                
                file->node = root;
                file->permissions = MODE_READ | MODE_WRITE | MODE_APPEND;
                file->open_read = false;
                file->open_write = false;
        }
        
        /* Add the filesystem info to the list of mounted filesystems */
        if (rc == EOK) {
                str_cpy(mtab_ent->mp, MAX_PATH_LEN, "fixme");
                str_cpy(mtab_ent->fs_name, FS_NAME_MAXLEN, fs_name);
                str_cpy(mtab_ent->opts, MAX_MNTOPTS_LEN, opts);
                mtab_ent->instance = instance;
                mtab_ent->service_id = service_id;

                link_initialize(&mtab_ent->link);

                fibril_mutex_lock(&mtab_list_lock);
                list_append(&mtab_ent->link, &mtab_list);
                mtab_size++;
                fibril_mutex_unlock(&mtab_list_lock);
        }       
        
        rc = EOK;

out:
        async_answer_1(rid, rc, rc == EOK ? fd : 0);

        if (opts) {
                free(opts);
        }
        if (fs_name) {
                free(fs_name);
        }
        if (mp) {
                vfs_file_put(mp);
        }
        if (file) {
                vfs_file_put(file);
        }
        if (rc != EOK && fd >= 0) {
                vfs_fd_free(fd);
        }
}

void vfs_unmount_srv(ipc_callid_t rid, ipc_call_t *request)
{
        int mpfd = IPC_GET_ARG1(*request);
        
        vfs_file_t *mp = vfs_file_get(mpfd);
        if (mp == NULL) {
                async_answer_0(rid, EBADF);
                return;
        }
        
        if (mp->node->mount == NULL) {
                async_answer_0(rid, ENOENT);
                vfs_file_put(mp);
                return;
        }
        
        fibril_rwlock_write_lock(&namespace_rwlock);
        
        /*
         * Count the total number of references for the mounted file system. We
         * are expecting at least one, which is held by the mount point.
         * If we find more, it means that
         * the file system cannot be gracefully unmounted at the moment because
         * someone is working with it.
         */
        if (vfs_nodes_refcount_sum_get(mp->node->mount->fs_handle, mp->node->mount->service_id) != 1) {
                async_answer_0(rid, EBUSY);
                vfs_file_put(mp);
                fibril_rwlock_write_unlock(&namespace_rwlock);
                return;
        }
        
        async_exch_t *exch = vfs_exchange_grab(mp->node->mount->fs_handle);
        int rc = async_req_1_0(exch, VFS_OUT_UNMOUNTED, mp->node->mount->service_id);
        vfs_exchange_release(exch);
        
        if (rc != EOK) {
                async_answer_0(rid, rc);
                vfs_file_put(mp);
                fibril_rwlock_write_unlock(&namespace_rwlock);
                return;
        }
        
        vfs_node_forget(mp->node->mount);
        vfs_node_put(mp->node);
        mp->node->mount = NULL;
        
        fibril_rwlock_write_unlock(&namespace_rwlock);
        
        fibril_mutex_lock(&mtab_list_lock);
        int found = 0;

        list_foreach(mtab_list, link, mtab_ent_t, mtab_ent) {
                // FIXME: mp name
                if (str_cmp(mtab_ent->mp, "fixme") == 0) {
                        list_remove(&mtab_ent->link);
                        mtab_size--;
                        free(mtab_ent);
                        found = 1;
                        break;
                }
        }
        assert(found);
        fibril_mutex_unlock(&mtab_list_lock);
        
        vfs_file_put(mp);
        async_answer_0(rid, EOK);
}

static inline bool walk_flags_valid(int flags)
{
        if ((flags&~WALK_ALL_FLAGS) != 0) {
                return false;
        }
        if ((flags&WALK_MAY_CREATE) && (flags&WALK_MUST_CREATE)) {
                return false;
        }
        if ((flags&WALK_REGULAR) && (flags&WALK_DIRECTORY)) {
                return false;
        }
        if ((flags&WALK_MAY_CREATE) || (flags&WALK_MUST_CREATE)) {
                if (!(flags&WALK_DIRECTORY) && !(flags&WALK_REGULAR)) {
                        return false;
                }
        }
        return true;
}

static inline int walk_lookup_flags(int flags)
{
        int lflags = 0;
        if (flags&WALK_MAY_CREATE || flags&WALK_MUST_CREATE) {
                lflags |= L_CREATE;
        }
        if (flags&WALK_MUST_CREATE) {
                lflags |= L_EXCLUSIVE;
        }
        if (flags&WALK_REGULAR) {
                lflags |= L_FILE;
        }
        if (flags&WALK_DIRECTORY) {
                lflags |= L_DIRECTORY;
        }
        if (flags&WALK_MOUNT_POINT) {
                lflags |= L_MP;
        }
        return lflags;
}

void vfs_walk(ipc_callid_t rid, ipc_call_t *request)
{
        /*
         * Parent is our relative root for file lookup.
         * For defined flags, see <ipc/vfs.h>.
         */
        int parentfd = IPC_GET_ARG1(*request);
        int flags = IPC_GET_ARG2(*request);
        
        if (!walk_flags_valid(flags)) {
                async_answer_0(rid, EINVAL);
                return;
        }
        
        char *path;
        int rc = async_data_write_accept((void **)&path, true, 0, 0, 0, NULL);
        
        /* Lookup the file structure corresponding to the file descriptor. */
        vfs_file_t *parent = vfs_file_get(parentfd);
        if (!parent) {
                free(path);
                async_answer_0(rid, EBADF);
                return;
        }
        
        fibril_rwlock_read_lock(&namespace_rwlock);
        
        vfs_lookup_res_t lr;
        rc = vfs_lookup_internal(parent->node, path, walk_lookup_flags(flags), &lr);
        free(path);

        if (rc != EOK) {
                fibril_rwlock_read_unlock(&namespace_rwlock);
                if (parent) {
                        vfs_file_put(parent);
                }
                async_answer_0(rid, rc);
                return;
        }
        
        vfs_node_t *node = vfs_node_get(&lr);
        
        vfs_file_t *file;
        int fd = vfs_fd_alloc(&file, false);
        if (fd < 0) {
                vfs_node_put(node);
                if (parent) {
                        vfs_file_put(parent);
                }
                async_answer_0(rid, fd);
                return;
        }
        assert(file != NULL);
        
        file->node = node;
        if (parent) {
                file->permissions = parent->permissions;
        } else {
                file->permissions = MODE_READ | MODE_WRITE | MODE_APPEND;
        }
        file->open_read = false;
        file->open_write = false;
        
        vfs_file_put(file);
        if (parent) {
                vfs_file_put(parent);
        }
        
        fibril_rwlock_read_unlock(&namespace_rwlock);

        async_answer_1(rid, EOK, fd);
}

void vfs_open2(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        int flags = IPC_GET_ARG2(*request);

        if (flags == 0) {
                async_answer_0(rid, EINVAL);
                return;
        }

        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(rid, EBADF);
                return;
        }
        
        if ((flags & ~file->permissions) != 0) {
                vfs_file_put(file);
                async_answer_0(rid, EPERM);
                return;
        }
        
        file->open_read = (flags & MODE_READ) != 0;
        file->open_write = (flags & (MODE_WRITE | MODE_APPEND)) != 0;
        file->append = (flags & MODE_APPEND) != 0;
        
        if (!file->open_read && !file->open_write) {
                vfs_file_put(file);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        if (file->node->type == VFS_NODE_DIRECTORY && file->open_write) {
                file->open_read = file->open_write = false;
                vfs_file_put(file);
                async_answer_0(rid, EINVAL);
                return;
        }
        
        int rc = vfs_open_node_remote(file->node);
        if (rc != EOK) {
                file->open_read = file->open_write = false;
                vfs_file_put(file);
                async_answer_0(rid, rc);
                return;
        }
        
        vfs_file_put(file);
        async_answer_0(rid, EOK);
}

void vfs_sync(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        
        /* Lookup the file structure corresponding to the file descriptor. */
        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(rid, ENOENT);
                return;
        }
        
        /*
         * Lock the open file structure so that no other thread can manipulate
         * the same open file at a time.
         */
        async_exch_t *fs_exch = vfs_exchange_grab(file->node->fs_handle);
        
        /* Make a VFS_OUT_SYMC request at the destination FS server. */
        aid_t msg;
        ipc_call_t answer;
        msg = async_send_2(fs_exch, VFS_OUT_SYNC, file->node->service_id,
            file->node->index, &answer);
        
        vfs_exchange_release(fs_exch);
        
        /* Wait for reply from the FS server. */
        sysarg_t rc;
        async_wait_for(msg, &rc);
        
        vfs_file_put(file);
        async_answer_0(rid, rc);
}

void vfs_close(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        int ret = vfs_fd_free(fd);
        async_answer_0(rid, ret);
}

typedef int (* rdwr_ipc_cb_t)(async_exch_t *, vfs_file_t *, ipc_call_t *,
    bool, void *);

static int rdwr_ipc_client(async_exch_t *exch, vfs_file_t *file,
    ipc_call_t *answer, bool read, void *data)
{
        size_t *bytes = (size_t *) data;
        int rc;

        /*
         * Make a VFS_READ/VFS_WRITE request at the destination FS server
         * and forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
         * destination FS server. The call will be routed as if sent by
         * ourselves. Note that call arguments are immutable in this case so we
         * don't have to bother.
         */

        if (read) {
                rc = async_data_read_forward_4_1(exch, VFS_OUT_READ,
                    file->node->service_id, file->node->index,
                    LOWER32(file->pos), UPPER32(file->pos), answer);
        } else {
                rc = async_data_write_forward_4_1(exch, VFS_OUT_WRITE,
                    file->node->service_id, file->node->index,
                    LOWER32(file->pos), UPPER32(file->pos), answer);
        }

        *bytes = IPC_GET_ARG1(*answer);
        return rc;
}

static int rdwr_ipc_internal(async_exch_t *exch, vfs_file_t *file,
    ipc_call_t *answer, bool read, void *data)
{
        rdwr_io_chunk_t *chunk = (rdwr_io_chunk_t *) data;

        if (exch == NULL)
                return ENOENT;
        
        aid_t msg = async_send_fast(exch, read ? VFS_OUT_READ : VFS_OUT_WRITE,
            file->node->service_id, file->node->index, LOWER32(file->pos),
            UPPER32(file->pos), answer);
        if (msg == 0)
                return EINVAL;

        int retval = async_data_read_start(exch, chunk->buffer, chunk->size);
        if (retval != EOK) {
                async_forget(msg);
                return retval;
        }
        
        sysarg_t rc;
        async_wait_for(msg, &rc);
        
        chunk->size = IPC_GET_ARG1(*answer); 

        return (int) rc;
}

static int vfs_rdwr(int fd, bool read, rdwr_ipc_cb_t ipc_cb, void *ipc_cb_data)
{
        /*
         * The following code strongly depends on the fact that the files data
         * structure can be only accessed by a single fibril and all file
         * operations are serialized (i.e. the reads and writes cannot
         * interleave and a file cannot be closed while it is being read).
         *
         * Additional synchronization needs to be added once the table of
         * open files supports parallel access!
         */
        
        /* Lookup the file structure corresponding to the file descriptor. */
        vfs_file_t *file = vfs_file_get(fd);
        if (!file)
                return EBADF;
        
        if ((read && !file->open_read) || (!read && !file->open_write)) {
                vfs_file_put(file);
                return EINVAL;
        }
        
        vfs_info_t *fs_info = fs_handle_to_info(file->node->fs_handle);
        assert(fs_info);
        
        bool rlock = read || ((fs_info->concurrent_read_write) && (fs_info->write_retains_size));
        
        /*
         * Lock the file's node so that no other client can read/write to it at
         * the same time unless the FS supports concurrent reads/writes and its
         * write implementation does not modify the file size.
         */
        if (rlock) {
                fibril_rwlock_read_lock(&file->node->contents_rwlock);
        } else {
                fibril_rwlock_write_lock(&file->node->contents_rwlock);
        }
        
        if (file->node->type == VFS_NODE_DIRECTORY) {
                /*
                 * Make sure that no one is modifying the namespace
                 * while we are in readdir().
                 */
                
                if (!read) {
                        if (rlock) {
                                fibril_rwlock_read_unlock(&file->node->contents_rwlock);
                        } else {
                                fibril_rwlock_write_unlock(&file->node->contents_rwlock);
                        }
                        vfs_file_put(file);
                        return EINVAL;
                }
                
                fibril_rwlock_read_lock(&namespace_rwlock);
        }
        
        async_exch_t *fs_exch = vfs_exchange_grab(file->node->fs_handle);
        
        if (!read && file->append)
                file->pos = file->node->size;
        
        /*
         * Handle communication with the endpoint FS.
         */
        ipc_call_t answer;
        int rc = ipc_cb(fs_exch, file, &answer, read, ipc_cb_data);
        
        vfs_exchange_release(fs_exch);
        
        size_t bytes = IPC_GET_ARG1(answer);
        
        if (file->node->type == VFS_NODE_DIRECTORY) {
                fibril_rwlock_read_unlock(&namespace_rwlock);
        }
        
        /* Unlock the VFS node. */
        if (rlock) {
                fibril_rwlock_read_unlock(&file->node->contents_rwlock);
        } else {
                /* Update the cached version of node's size. */
                if (rc == EOK) {
                        file->node->size = MERGE_LOUP32(IPC_GET_ARG2(answer),
                            IPC_GET_ARG3(answer));
                }
                fibril_rwlock_write_unlock(&file->node->contents_rwlock);
        }
        
        /* Update the position pointer and unlock the open file. */
        if (rc == EOK) {
                file->pos += bytes;
        }
        vfs_file_put(file);     

        return rc;
}
        
static void vfs_rdwr_client(ipc_callid_t rid, ipc_call_t *request, bool read)
{
        size_t bytes = 0;       
        int rc = vfs_rdwr(IPC_GET_ARG1(*request), read, rdwr_ipc_client,
            &bytes);
        async_answer_1(rid, rc, bytes);
}

int vfs_rdwr_internal(int fd, bool read, rdwr_io_chunk_t *chunk)
{
        return vfs_rdwr(fd, read, rdwr_ipc_internal, chunk);
}

void vfs_read(ipc_callid_t rid, ipc_call_t *request)
{
        vfs_rdwr_client(rid, request, true);
}

void vfs_write(ipc_callid_t rid, ipc_call_t *request)
{
        vfs_rdwr_client(rid, request, false);
}

void vfs_seek(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = (int) IPC_GET_ARG1(*request);
        off64_t off = (off64_t) MERGE_LOUP32(IPC_GET_ARG2(*request),
            IPC_GET_ARG3(*request));
        int whence = (int) IPC_GET_ARG4(*request);
        
        /* Lookup the file structure corresponding to the file descriptor. */
        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(rid, ENOENT);
                return;
        }
        
        off64_t newoff;
        switch (whence) {
        case SEEK_SET:
                if (off >= 0) {
                        file->pos = (aoff64_t) off;
                        vfs_file_put(file);
                        async_answer_1(rid, EOK, off);
                        return;
                }
                break;
        case SEEK_CUR:
                if ((off >= 0) && (file->pos + off < file->pos)) {
                        vfs_file_put(file);
                        async_answer_0(rid, EOVERFLOW);
                        return;
                }
                
                if ((off < 0) && (file->pos < (aoff64_t) -off)) {
                        vfs_file_put(file);
                        async_answer_0(rid, EOVERFLOW);
                        return;
                }
                
                file->pos += off;
                newoff = (file->pos > OFF64_MAX) ? OFF64_MAX : file->pos;
                
                vfs_file_put(file);
                async_answer_2(rid, EOK, LOWER32(newoff),
                    UPPER32(newoff));
                return;
        case SEEK_END:
                fibril_rwlock_read_lock(&file->node->contents_rwlock);
                aoff64_t size = vfs_node_get_size(file->node);
                
                if ((off >= 0) && (size + off < size)) {
                        fibril_rwlock_read_unlock(&file->node->contents_rwlock);
                        vfs_file_put(file);
                        async_answer_0(rid, EOVERFLOW);
                        return;
                }
                
                if ((off < 0) && (size < (aoff64_t) -off)) {
                        fibril_rwlock_read_unlock(&file->node->contents_rwlock);
                        vfs_file_put(file);
                        async_answer_0(rid, EOVERFLOW);
                        return;
                }
                
                file->pos = size + off;
                newoff = (file->pos > OFF64_MAX) ?  OFF64_MAX : file->pos;
                
                fibril_rwlock_read_unlock(&file->node->contents_rwlock);
                vfs_file_put(file);
                async_answer_2(rid, EOK, LOWER32(newoff), UPPER32(newoff));
                return;
        }
        
        vfs_file_put(file);
        async_answer_0(rid, EINVAL);
}

int vfs_truncate_internal(fs_handle_t fs_handle, service_id_t service_id,
    fs_index_t index, aoff64_t size)
{
        async_exch_t *exch = vfs_exchange_grab(fs_handle);
        sysarg_t rc = async_req_4_0(exch, VFS_OUT_TRUNCATE,
            (sysarg_t) service_id, (sysarg_t) index, LOWER32(size),
            UPPER32(size));
        vfs_exchange_release(exch);
        
        return (int) rc;
}

void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        aoff64_t size = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG2(*request),
            IPC_GET_ARG3(*request));
        int rc;

        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(rid, ENOENT);
                return;
        }

        fibril_rwlock_write_lock(&file->node->contents_rwlock);
        rc = vfs_truncate_internal(file->node->fs_handle,
            file->node->service_id, file->node->index, size);
        if (rc == EOK)
                file->node->size = size;
        fibril_rwlock_write_unlock(&file->node->contents_rwlock);

        vfs_file_put(file);
        async_answer_0(rid, (sysarg_t)rc);
}

void vfs_fstat(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        sysarg_t rc;

        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(rid, ENOENT);
                return;
        }
        assert(file->node);

        ipc_callid_t callid;
        if (!async_data_read_receive(&callid, NULL)) {
                vfs_file_put(file);
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }

        async_exch_t *exch = vfs_exchange_grab(file->node->fs_handle);
        assert(exch);
        
        aid_t msg;
        msg = async_send_3(exch, VFS_OUT_STAT, file->node->service_id,
            file->node->index, true, NULL);
        assert(msg);
        async_forward_fast(callid, exch, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
        
        vfs_exchange_release(exch);
        
        async_wait_for(msg, &rc);
        
        vfs_file_put(file);
        async_answer_0(rid, rc);
}

static void out_destroy(vfs_triplet_t *file)
{
        async_exch_t *exch = vfs_exchange_grab(file->fs_handle);
        async_msg_2(exch, VFS_OUT_DESTROY,
                (sysarg_t) file->service_id, (sysarg_t) file->index);
        vfs_exchange_release(exch);
}

void vfs_unlink2(ipc_callid_t rid, ipc_call_t *request)
{
        int rc;
        char *path;
        vfs_file_t *parent = NULL;
        vfs_file_t *expect = NULL;
        
        int parentfd = IPC_GET_ARG1(*request);
        int expectfd = IPC_GET_ARG2(*request);
        int wflag = IPC_GET_ARG3(*request);
        
        rc = async_data_write_accept((void **) &path, true, 0, 0, 0, NULL);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                return;
        }
        if (parentfd == expectfd) {
                async_answer_0(rid, EINVAL);
                return;
        }
        
        fibril_rwlock_write_lock(&namespace_rwlock);
        
        int lflag = (wflag&WALK_DIRECTORY) ? L_DIRECTORY: 0;

        /* Files are retrieved in order of file descriptors, to prevent deadlock. */
        if (parentfd < expectfd) {
                parent = vfs_file_get(parentfd);
                if (!parent) {
                        rc = EBADF;
                        goto exit;
                }
        }
        
        if (expectfd >= 0) {
                expect = vfs_file_get(expectfd);
                if (!expect) {
                        rc = ENOENT;
                        goto exit;
                }
        }
        
        if (parentfd > expectfd) {
                parent = vfs_file_get(parentfd);
                if (!parent) {
                        rc = EBADF;
                        goto exit;
                }
        }
        
        assert(parent != NULL);
        
        if (expectfd >= 0) {
                vfs_lookup_res_t lr;
                rc = vfs_lookup_internal(parent->node, path, lflag, &lr);
                if (rc != EOK) {
                        goto exit;
                }
                
                vfs_node_t *found_node = vfs_node_peek(&lr);            
                if (expect->node != found_node) {
                        rc = ENOENT;
                        goto exit;
                }
                
                vfs_file_put(expect);
                expect = NULL;
        }
        
        vfs_lookup_res_t lr;
        rc = vfs_lookup_internal(parent->node, path, lflag | L_UNLINK, &lr);
        if (rc != EOK) {
                goto exit;
        }

        /* If the node is not held by anyone, try to destroy it. */
        if (vfs_node_peek(&lr) == NULL) {
                out_destroy(&lr.triplet);
        }

exit:
        if (path) {
                free(path);
        }
        if (parent) {
                vfs_file_put(parent);
        }
        if (expect) {
                vfs_file_put(expect);
        }
        fibril_rwlock_write_unlock(&namespace_rwlock);
        async_answer_0(rid, rc);
}

static size_t shared_path(char *a, char *b)
{
        size_t res = 0;
        
        while (a[res] == b[res] && a[res] != 0) {
                res++;
        }
        
        if (a[res] == b[res]) {
                return res;
        }
        
        res--;
        while (a[res] != '/') {
                res--;
        }
        return res;
}

static int vfs_rename_internal(vfs_node_t *base, char *old, char *new)
{
        assert(base != NULL);
        assert(old != NULL);
        assert(new != NULL);
        
        vfs_lookup_res_t base_lr;
        vfs_lookup_res_t old_lr;
        vfs_lookup_res_t new_lr_orig;
        bool orig_unlinked = false;
        
        int rc;
        
        size_t shared = shared_path(old, new);
        
        /* Do not allow one path to be a prefix of the other. */
        if (old[shared] == 0 || new[shared] == 0) {
                return EINVAL;
        }
        assert(old[shared] == '/');
        assert(new[shared] == '/');
        
        fibril_rwlock_write_lock(&namespace_rwlock);
        
        /* Resolve the shared portion of the path first. */
        if (shared != 0) {
                old[shared] = 0;
                rc = vfs_lookup_internal(base, old, L_DIRECTORY, &base_lr);
                if (rc != EOK) {
                        fibril_rwlock_write_unlock(&namespace_rwlock);
                        return rc;
                }
                
                base = vfs_node_get(&base_lr);
                old[shared] = '/';
                old += shared;
                new += shared;
        } else {
                vfs_node_addref(base);
        }
        
        
        rc = vfs_lookup_internal(base, new, L_UNLINK | L_DISABLE_MOUNTS, &new_lr_orig);
        if (rc == EOK) {
                orig_unlinked = true;
        } else if (rc != ENOENT) {
                vfs_node_put(base);
                fibril_rwlock_write_unlock(&namespace_rwlock);
                return rc;
        }
        
        rc = vfs_lookup_internal(base, old, L_UNLINK | L_DISABLE_MOUNTS, &old_lr);
        if (rc != EOK) {
                if (orig_unlinked) {
                        vfs_link_internal(base, new, &new_lr_orig.triplet);
                }
                vfs_node_put(base);
                fibril_rwlock_write_unlock(&namespace_rwlock);
                return rc;
        }
        
        rc = vfs_link_internal(base, new, &old_lr.triplet);
        if (rc != EOK) {
                vfs_link_internal(base, old, &old_lr.triplet);
                if (orig_unlinked) {
                        vfs_link_internal(base, new, &new_lr_orig.triplet);
                }
                vfs_node_put(base);
                fibril_rwlock_write_unlock(&namespace_rwlock);
                return rc;
        }
        
        /* If the node is not held by anyone, try to destroy it. */
        if (orig_unlinked && vfs_node_peek(&new_lr_orig) == NULL) {
                out_destroy(&new_lr_orig.triplet);
        }
        
        vfs_node_put(base);
        fibril_rwlock_write_unlock(&namespace_rwlock);
        return EOK;
}

void vfs_rename(ipc_callid_t rid, ipc_call_t *request)
{
        /* The common base directory. */
        int basefd;
        char *old = NULL;
        char *new = NULL;
        vfs_file_t *base = NULL;
        int rc;
        
        basefd = IPC_GET_ARG1(*request);
        
        /* Retrieve the old path. */
        rc = async_data_write_accept((void **) &old, true, 0, 0, 0, NULL);
        if (rc != EOK) {
                goto out;
        }
        
        /* Retrieve the new path. */
        rc = async_data_write_accept((void **) &new, true, 0, 0, 0, NULL);
        if (rc != EOK) {
                goto out;
        }
        
        size_t olen;
        size_t nlen;
        char *oldc = canonify(old, &olen);
        char *newc = canonify(new, &nlen);
        
        if ((!oldc) || (!newc)) {
                rc = EINVAL;
                goto out;
        }
        
        assert(oldc[olen] == '\0');
        assert(newc[nlen] == '\0');
        
        /* Lookup the file structure corresponding to the file descriptor. */
        base = vfs_file_get(basefd);
        if (!base) {
                rc = EBADF;
                goto out;
        }
        
        rc = vfs_rename_internal(base->node, oldc, newc);

out:
        async_answer_0(rid, rc);

        if (old) {
                free(old);
        }
        if (new) {
                free(new);
        }
        if (base) {
                vfs_file_put(base);
        }
}

void vfs_dup(ipc_callid_t rid, ipc_call_t *request)
{
        int oldfd = IPC_GET_ARG1(*request);
        int newfd = IPC_GET_ARG2(*request);
        
        /* If the file descriptors are the same, do nothing. */
        if (oldfd == newfd) {
                async_answer_1(rid, EOK, newfd);
                return;
        }
        
        /* Lookup the file structure corresponding to oldfd. */
        vfs_file_t *oldfile = vfs_file_get(oldfd);
        if (!oldfile) {
                async_answer_0(rid, EBADF);
                return;
        }
        
        /* Make sure newfd is closed. */
        (void) vfs_fd_free(newfd);
        
        /* Assign the old file to newfd. */
        int ret = vfs_fd_assign(oldfile, newfd);
        vfs_file_put(oldfile);
        
        if (ret != EOK)
                async_answer_0(rid, ret);
        else
                async_answer_1(rid, EOK, newfd);
}

void vfs_wait_handle(ipc_callid_t rid, ipc_call_t *request)
{
        bool high_fd = IPC_GET_ARG1(*request);
        int fd = vfs_wait_handle_internal(high_fd);
        async_answer_1(rid, EOK, fd);
}

void vfs_get_mtab(ipc_callid_t rid, ipc_call_t *request)
{
        ipc_callid_t callid;
        ipc_call_t data;
        sysarg_t rc = EOK;
        size_t len;

        fibril_mutex_lock(&mtab_list_lock);

        /* Send to the caller the number of mounted filesystems */
        callid = async_get_call(&data);
        if (IPC_GET_IMETHOD(data) != VFS_IN_PING) {
                rc = ENOTSUP;
                async_answer_0(callid, rc);
                goto exit;
        }
        async_answer_1(callid, EOK, mtab_size);

        list_foreach(mtab_list, link, mtab_ent_t, mtab_ent) {
                rc = ENOTSUP;

                if (!async_data_read_receive(&callid, &len)) {
                        async_answer_0(callid, rc);
                        goto exit;
                }

                (void) async_data_read_finalize(callid, mtab_ent->mp,
                    str_size(mtab_ent->mp));

                if (!async_data_read_receive(&callid, &len)) {
                        async_answer_0(callid, rc);
                        goto exit;
                }

                (void) async_data_read_finalize(callid, mtab_ent->opts,
                    str_size(mtab_ent->opts));

                if (!async_data_read_receive(&callid, &len)) {
                        async_answer_0(callid, rc);
                        goto exit;
                }

                (void) async_data_read_finalize(callid, mtab_ent->fs_name,
                    str_size(mtab_ent->fs_name));

                callid = async_get_call(&data);

                if (IPC_GET_IMETHOD(data) != VFS_IN_PING) {
                        async_answer_0(callid, rc);
                        goto exit;
                }

                rc = EOK;
                async_answer_2(callid, rc, mtab_ent->instance,
                    mtab_ent->service_id);
        }

exit:
        fibril_mutex_unlock(&mtab_list_lock);
        async_answer_0(rid, rc);
}

void vfs_statfs(ipc_callid_t rid, ipc_call_t *request)
{
        int fd = IPC_GET_ARG1(*request);
        
        ipc_callid_t callid;
        if (!async_data_read_receive(&callid, NULL)) {
                async_answer_0(callid, EINVAL);
                async_answer_0(rid, EINVAL);
                return;
        }

        vfs_file_t *file = vfs_file_get(fd);
        if (!file) {
                async_answer_0(callid, EBADF);
                async_answer_0(rid, EBADF);
        }

        vfs_node_t *node = file->node;

        async_exch_t *exch = vfs_exchange_grab(node->fs_handle);
        
        aid_t msg;
        msg = async_send_3(exch, VFS_OUT_STATFS, node->service_id,
            node->index, false, NULL);
        async_forward_fast(callid, exch, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
        
        vfs_exchange_release(exch);
        
        sysarg_t rv;
        async_wait_for(msg, &rv);

        vfs_file_put(file);

        async_answer_0(rid, rv);
}

void vfs_op_clone(ipc_callid_t rid, ipc_call_t *request)
{
        int oldfd = IPC_GET_ARG1(*request);
        bool desc = IPC_GET_ARG2(*request);
        
        /* Lookup the file structure corresponding to fd. */
        vfs_file_t *oldfile = vfs_file_get(oldfd);
        if (oldfile == NULL) {
                async_answer_0(rid, EBADF);
                return;
        }
        
        vfs_file_t *newfile;
        int newfd = vfs_fd_alloc(&newfile, desc);
        async_answer_0(rid, newfd);
        
        if (newfd < 0) {
                vfs_file_put(oldfile);
                return;
        }
        
        assert(oldfile->node != NULL);
        
        newfile->node = oldfile->node;
        newfile->permissions = oldfile->permissions;
        vfs_node_addref(newfile->node);

        vfs_file_put(oldfile);
        vfs_file_put(newfile);
}

/**
 * @}
 */