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	vfs_ops.c

 * @brief	Operations that VFS offers to its clients.

 */

#include "vfs.h"

#include <ipc/ipc.h>

#include <async.h>

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <bool.h>

#include <futex.h>

#include <rwlock.h>

#include <libadt/list.h>

#include <unistd.h>

#include <ctype.h>

#include <fcntl.h>

#include <assert.h>

#include <vfs/canonify.h>

/* Forward declarations of static functions. */

static int vfs_truncate_internal(fs_handle_t, dev_handle_t, fs_index_t, size_t);

/**

 * This rwlock prevents the race between a triplet-to-VFS-node resolution and a

 * concurrent VFS operation which modifies the file system namespace.

 */

RWLOCK_INITIALIZE(namespace_rwlock);

futex_t rootfs_futex = FUTEX_INITIALIZER;

vfs_triplet_t rootfs = {

	.fs_handle = 0,

	.dev_handle = 0,

	.index = 0,

};

static int

lookup_root(fs_handle_t fs_handle, dev_handle_t dev_handle,

    vfs_lookup_res_t *result)

{

	vfs_pair_t altroot = {

		.fs_handle = fs_handle,

		.dev_handle = dev_handle,

	};

	return vfs_lookup_internal("/", L_DIRECTORY, result, &altroot);

}

void vfs_mount(ipc_callid_t rid, ipc_call_t *request)

{

	dev_handle_t dev_handle;

	vfs_node_t *mp_node = NULL;

	int rc;

	/*

	 * 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.

	 */

	dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

	/*

	 * For now, don't make use of ARG2 and ARG3, but they can be used to

	 * carry mount options in the future.

	 */

	ipc_callid_t callid;

	size_t size;

	/*

	 * Now, we expect the client to send us data with the name of the file

	 * system.

	 */

	if (!ipc_data_write_receive(&callid, &size)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/*

	 * Don't receive more than is necessary for storing a full file system

	 * name.

	 */

	if (size < 1 || size > FS_NAME_MAXLEN) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/* Deliver the file system name. */

	char fs_name[FS_NAME_MAXLEN + 1];

	(void) ipc_data_write_finalize(callid, fs_name, size);

	fs_name[size] = '\0';

	/*

	 * Check if we know a file system with the same name as is in fs_name.

	 * This will also give us its file system handle.

	 */

	fs_handle_t fs_handle = fs_name_to_handle(fs_name, true);

	if (!fs_handle) {

		ipc_answer_0(rid, ENOENT);

		return;

	}

	/* Now, we want the client to send us the mount point. */

	if (!ipc_data_write_receive(&callid, &size)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/* Check whether size is reasonable wrt. the mount point. */

	if (size < 1 || size > MAX_PATH_LEN) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/* Allocate buffer for the mount point data being received. */

	uint8_t *buf;

	buf = malloc(size + 1);

	if (!buf) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	/* Deliver the mount point. */

	(void) ipc_data_write_finalize(callid, buf, size);

	buf[size] = '\0';

	/*

	 * Lookup the root node of the filesystem being mounted.

	 * In this case, we don't need to take the namespace_futex as the root

	 * node cannot be removed. However, we do take a reference to it so

	 * that we can track how many times it has been mounted.

	 */

	vfs_lookup_res_t mr_res;

	rc = lookup_root(fs_handle, dev_handle, &mr_res);

	if (rc != EOK) {

		free(buf);

		ipc_answer_0(rid, rc);

		return;

	}

	vfs_node_t *mr_node = vfs_node_get(&mr_res);

	if (!mr_node) {

		free(buf);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	/* Finally, we need to resolve the path to the mountpoint. */

	vfs_lookup_res_t mp_res;

	futex_down(&rootfs_futex);

	if (rootfs.fs_handle) {

		/* We already have the root FS. */

		rwlock_write_lock(&namespace_rwlock);

		if ((size == 1) && (buf[0] == '/')) {

			/* Trying to mount root FS over root FS */

			rwlock_write_unlock(&namespace_rwlock);

			futex_up(&rootfs_futex);

			vfs_node_put(mr_node);

			free(buf);

			ipc_answer_0(rid, EBUSY);

			return;

		}

		rc = vfs_lookup_internal(buf, L_DIRECTORY, &mp_res, NULL);

		if (rc != EOK) {

			/* The lookup failed for some reason. */

			rwlock_write_unlock(&namespace_rwlock);

			futex_up(&rootfs_futex);

			vfs_node_put(mr_node);	/* failed -> drop reference */

			free(buf);

			ipc_answer_0(rid, rc);

			return;

		}

		mp_node = vfs_node_get(&mp_res);

		if (!mp_node) {

			rwlock_write_unlock(&namespace_rwlock);

			futex_up(&rootfs_futex);

			vfs_node_put(mr_node);	/* failed -> drop reference */

			free(buf);

			ipc_answer_0(rid, ENOMEM);

			return;

		}

		/*

		 * Now we hold a reference to mp_node.

		 * It will be dropped upon the corresponding VFS_UNMOUNT.

		 * This prevents the mount point from being deleted.

		 */

		rwlock_write_unlock(&namespace_rwlock);

	} else {

		/* We still don't have the root file system mounted. */

		if ((size == 1) && (buf[0] == '/')) {

			/* For this simple, but important case, we are done. */

			rootfs = mr_res.triplet;

			futex_up(&rootfs_futex);

			free(buf);

			ipc_answer_0(rid, EOK);

			return;

		} else {

			/*

			 * We can't resolve this without the root filesystem

			 * being mounted first.

			 */

			futex_up(&rootfs_futex);

			free(buf);

			vfs_node_put(mr_node);	/* failed -> drop reference */

			ipc_answer_0(rid, ENOENT);

			return;

		}

	}

	futex_up(&rootfs_futex);

	free(buf);	/* The buffer is not needed anymore. */

	/*

	 * At this point, we have all necessary pieces: file system and device

	 * handles, and we know the mount point VFS node and also the root node

	 * of the file system being mounted.

	 */

	/**

	 * @todo

	 * Add more IPC parameters so that we can send mount mode/flags.

	 */

	int phone = vfs_grab_phone(mp_res.triplet.fs_handle);

	rc = async_req_5_0(phone, VFS_MOUNT,

	    (ipcarg_t) mp_res.triplet.dev_handle,

	    (ipcarg_t) mp_res.triplet.index,

	    (ipcarg_t) mr_res.triplet.fs_handle,

	    (ipcarg_t) mr_res.triplet.dev_handle,

	    (ipcarg_t) mr_res.triplet.index);

	vfs_release_phone(phone);

	if (rc != EOK) {

		/* Mount failed, drop references to mr_node and mp_node. */

		vfs_node_put(mr_node);

		if (mp_node)

			vfs_node_put(mp_node);

	}

	ipc_answer_0(rid, rc);

}

void vfs_open(ipc_callid_t rid, ipc_call_t *request)

{

	if (!vfs_files_init()) {

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	/*

	 * The POSIX interface is open(path, oflag, mode).

	 * We can receive oflags and mode along with the VFS_OPEN call; the path

	 * will need to arrive in another call.

	 *

	 * We also receive one private, non-POSIX set of flags called lflag

	 * used to pass information to vfs_lookup_internal().

	 */

	int lflag = IPC_GET_ARG1(*request);

	int oflag = IPC_GET_ARG2(*request);

	int mode = IPC_GET_ARG3(*request);

	size_t len;

	if (oflag & O_CREAT)

		lflag |= L_CREATE;

	if (oflag & O_EXCL)

		lflag |= L_EXCLUSIVE;

	ipc_callid_t callid;

	if (!ipc_data_write_receive(&callid, &len)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	char *path = malloc(len + 1);

	if (!path) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	int rc;

	if ((rc = ipc_data_write_finalize(callid, path, len))) {

		ipc_answer_0(rid, rc);

		free(path);

		return;

	}

	path[len] = '\0';

	/*

	 * Avoid the race condition in which the file can be deleted before we

	 * find/create-and-lock the VFS node corresponding to the looked-up

	 * triplet.

	 */

	if (lflag & L_CREATE)

		rwlock_write_lock(&namespace_rwlock);

	else

		rwlock_read_lock(&namespace_rwlock);

	/* The path is now populated and we can call vfs_lookup_internal(). */

	vfs_lookup_res_t lr;

	rc = vfs_lookup_internal(path, lflag, &lr, NULL);

	if (rc) {

		if (lflag & L_CREATE)

			rwlock_write_unlock(&namespace_rwlock);

		else

			rwlock_read_unlock(&namespace_rwlock);

		ipc_answer_0(rid, rc);

		free(path);

		return;

	}

	/* Path is no longer needed. */

	free(path);

	vfs_node_t *node = vfs_node_get(&lr);

	if (lflag & L_CREATE)

		rwlock_write_unlock(&namespace_rwlock);

	else

		rwlock_read_unlock(&namespace_rwlock);

	/* Truncate the file if requested and if necessary. */

	if (oflag & O_TRUNC) {

		rwlock_write_lock(&node->contents_rwlock);

		if (node->size) {

			rc = vfs_truncate_internal(node->fs_handle,

			    node->dev_handle, node->index, 0);

			if (rc) {

				rwlock_write_unlock(&node->contents_rwlock);

				vfs_node_put(node);

				ipc_answer_0(rid, rc);

				return;

			}

			node->size = 0;

		}

		rwlock_write_unlock(&node->contents_rwlock);

	}

	/*

	 * Get ourselves a file descriptor and the corresponding vfs_file_t

	 * structure.

	 */

	int fd = vfs_fd_alloc();

	if (fd < 0) {

		vfs_node_put(node);

		ipc_answer_0(rid, fd);

		return;

	}

	vfs_file_t *file = vfs_file_get(fd);

	file->node = node;

	if (oflag & O_APPEND) 

		file->append = true;

	/*

	 * The following increase in reference count is for the fact that the

	 * file is being opened and that a file structure is pointing to it.

	 * It is necessary so that the file will not disappear when

	 * vfs_node_put() is called. The reference will be dropped by the

	 * respective VFS_CLOSE.

	 */

	vfs_node_addref(node);

	vfs_node_put(node);

	/* Success! Return the new file descriptor to the client. */

	ipc_answer_1(rid, EOK, fd);

}

void vfs_close(ipc_callid_t rid, ipc_call_t *request)

{

	int fd = IPC_GET_ARG1(*request);

	if (fd >= MAX_OPEN_FILES) {

		ipc_answer_0(rid, EBADF);

		return;

	}

	vfs_fd_free(fd);

	ipc_answer_0(rid, EOK);

}

static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)

{

	/*

	 * 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!

	 */

	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) {

		ipc_answer_0(rid, ENOENT);

		return;

	}

	/*

	 * Now we need to receive a call with client's

	 * IPC_M_DATA_READ/IPC_M_DATA_WRITE request.

	 */

	ipc_callid_t callid;

	int res;

	if (read)

		res = ipc_data_read_receive(&callid, NULL);

	else 

		res = ipc_data_write_receive(&callid, NULL);

	if (!res) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	/*

	 * Lock the open file structure so that no other thread can manipulate

	 * the same open file at a time.

	 */

	futex_down(&file->lock);

	/*

	 * Lock the file's node so that no other client can read/write to it at

	 * the same time.

	 */

	if (read)

		rwlock_read_lock(&file->node->contents_rwlock);

	else

		rwlock_write_lock(&file->node->contents_rwlock);

	int fs_phone = vfs_grab_phone(file->node->fs_handle);	

	/* Make a VFS_READ/VFS_WRITE request at the destination FS server. */

	aid_t msg;

	ipc_call_t answer;

	if (!read && file->append)

		file->pos = file->node->size;

	msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),

	    file->node->dev_handle, file->node->index, file->pos, &answer);

	/*

	 * 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.

	 */

	ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);

	vfs_release_phone(fs_phone);

	/* Wait for reply from the FS server. */

	ipcarg_t rc;

	async_wait_for(msg, &rc);

	size_t bytes = IPC_GET_ARG1(answer);

	/* Unlock the VFS node. */

	if (read)

		rwlock_read_unlock(&file->node->contents_rwlock);

	else {

		/* Update the cached version of node's size. */

		if (rc == EOK)

			file->node->size = IPC_GET_ARG2(answer); 

		rwlock_write_unlock(&file->node->contents_rwlock);

	}

	/* Update the position pointer and unlock the open file. */

	if (rc == EOK)

		file->pos += bytes;

	futex_up(&file->lock);

	/*

	 * FS server's reply is the final result of the whole operation we

	 * return to the client.

	 */

	ipc_answer_1(rid, rc, bytes);

}

void vfs_read(ipc_callid_t rid, ipc_call_t *request)

{

	vfs_rdwr(rid, request, true);

}

void vfs_write(ipc_callid_t rid, ipc_call_t *request)

{

	vfs_rdwr(rid, request, false);

}

void vfs_seek(ipc_callid_t rid, ipc_call_t *request)

{

	int fd = (int) IPC_GET_ARG1(*request);

	off_t off = (off_t) IPC_GET_ARG2(*request);

	int whence = (int) IPC_GET_ARG3(*request);

	/* Lookup the file structure corresponding to the file descriptor. */

	vfs_file_t *file = vfs_file_get(fd);

	if (!file) {

		ipc_answer_0(rid, ENOENT);

		return;

	}

	off_t newpos;

	futex_down(&file->lock);

	if (whence == SEEK_SET) {

		file->pos = off;

		futex_up(&file->lock);

		ipc_answer_1(rid, EOK, off);

		return;

	}

	if (whence == SEEK_CUR) {

		if (file->pos + off < file->pos) {

			futex_up(&file->lock);

			ipc_answer_0(rid, EOVERFLOW);

			return;

		}

		file->pos += off;

		newpos = file->pos;

		futex_up(&file->lock);

		ipc_answer_1(rid, EOK, newpos);

		return;

	}

	if (whence == SEEK_END) {

		rwlock_read_lock(&file->node->contents_rwlock);

		size_t size = file->node->size;

		rwlock_read_unlock(&file->node->contents_rwlock);

		if (size + off < size) {

			futex_up(&file->lock);

			ipc_answer_0(rid, EOVERFLOW);

			return;

		}

		newpos = size + off;

		futex_up(&file->lock);

		ipc_answer_1(rid, EOK, newpos);

		return;

	}

	futex_up(&file->lock);

	ipc_answer_0(rid, EINVAL);

}

int

vfs_truncate_internal(fs_handle_t fs_handle, dev_handle_t dev_handle,

    fs_index_t index, size_t size)

{

	ipcarg_t rc;

	int fs_phone;

	fs_phone = vfs_grab_phone(fs_handle);

	rc = async_req_3_0(fs_phone, VFS_TRUNCATE, (ipcarg_t)dev_handle,

	    (ipcarg_t)index, (ipcarg_t)size);

	vfs_release_phone(fs_phone);

	return (int)rc;

}

void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)

{

	int fd = IPC_GET_ARG1(*request);

	size_t size = IPC_GET_ARG2(*request);

	int rc;

	vfs_file_t *file = vfs_file_get(fd);

	if (!file) {

		ipc_answer_0(rid, ENOENT);

		return;

	}

	futex_down(&file->lock);

	rwlock_write_lock(&file->node->contents_rwlock);

	rc = vfs_truncate_internal(file->node->fs_handle,

	    file->node->dev_handle, file->node->index, size);

	if (rc == EOK)

		file->node->size = size;

	rwlock_write_unlock(&file->node->contents_rwlock);

	futex_up(&file->lock);

	ipc_answer_0(rid, (ipcarg_t)rc);

}

void vfs_mkdir(ipc_callid_t rid, ipc_call_t *request)

{

	int mode = IPC_GET_ARG1(*request);

	size_t len;

	ipc_callid_t callid;

	if (!ipc_data_write_receive(&callid, &len)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	char *path = malloc(len + 1);

	if (!path) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	int rc;

	if ((rc = ipc_data_write_finalize(callid, path, len))) {

		ipc_answer_0(rid, rc);

		free(path);

		return;

	}

	path[len] = '\0';

	rwlock_write_lock(&namespace_rwlock);

	int lflag = L_DIRECTORY | L_CREATE | L_EXCLUSIVE;

	rc = vfs_lookup_internal(path, lflag, NULL, NULL);

	rwlock_write_unlock(&namespace_rwlock);

	free(path);

	ipc_answer_0(rid, rc);

}

void vfs_unlink(ipc_callid_t rid, ipc_call_t *request)

{

	int lflag = IPC_GET_ARG1(*request);

	size_t len;

	ipc_callid_t callid;

	if (!ipc_data_write_receive(&callid, &len)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	char *path = malloc(len + 1);

	if (!path) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	int rc;

	if ((rc = ipc_data_write_finalize(callid, path, len))) {

		ipc_answer_0(rid, rc);

		free(path);

		return;

	}

	path[len] = '\0';

	rwlock_write_lock(&namespace_rwlock);

	lflag &= L_DIRECTORY;	/* sanitize lflag */

	vfs_lookup_res_t lr;

	rc = vfs_lookup_internal(path, lflag | L_UNLINK, &lr, NULL);

	free(path);

	if (rc != EOK) {

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, rc);

		return;

	}

	/*

	 * The name has already been unlinked by vfs_lookup_internal().

	 * We have to get and put the VFS node to ensure that it is

	 * VFS_DESTROY'ed after the last reference to it is dropped.

	 */

	vfs_node_t *node = vfs_node_get(&lr);

	futex_down(&nodes_futex);

	node->lnkcnt--;

	futex_up(&nodes_futex);

	rwlock_write_unlock(&namespace_rwlock);

	vfs_node_put(node);

	ipc_answer_0(rid, EOK);

}

void vfs_rename(ipc_callid_t rid, ipc_call_t *request)

{

	size_t len;

	ipc_callid_t callid;

	int rc;

	/* Retrieve the old path. */

	if (!ipc_data_write_receive(&callid, &len)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		return;

	}

	char *old = malloc(len + 1);

	if (!old) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		return;

	}

	if ((rc = ipc_data_write_finalize(callid, old, len))) {

		ipc_answer_0(rid, rc);

		free(old);

		return;

	}

	old[len] = '\0';

	/* Retrieve the new path. */

	if (!ipc_data_write_receive(&callid, &len)) {

		ipc_answer_0(callid, EINVAL);

		ipc_answer_0(rid, EINVAL);

		free(old);

		return;

	}

	char *new = malloc(len + 1);

	if (!new) {

		ipc_answer_0(callid, ENOMEM);

		ipc_answer_0(rid, ENOMEM);

		free(old);

		return;

	}

	if ((rc = ipc_data_write_finalize(callid, new, len))) {

		ipc_answer_0(rid, rc);

		free(old);

		free(new);

		return;

	}

	new[len] = '\0';

	char *oldc = canonify(old, &len);

	char *newc = canonify(new, NULL);

	if (!oldc || !newc) {

		ipc_answer_0(rid, EINVAL);

		free(old);

		free(new);

		return;

	}

	if (!strncmp(newc, oldc, len)) {

		/* oldc is a prefix of newc */

		ipc_answer_0(rid, EINVAL);

		free(old);

		free(new);

		return;

	}

	vfs_lookup_res_t old_lr;

	vfs_lookup_res_t new_lr;

	vfs_lookup_res_t new_par_lr;

	rwlock_write_lock(&namespace_rwlock);

	/* Lookup the node belonging to the old file name. */

	rc = vfs_lookup_internal(oldc, L_NONE, &old_lr, NULL);

	if (rc != EOK) {

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, rc);

		free(old);

		free(new);

		return;

	}

	vfs_node_t *old_node = vfs_node_get(&old_lr);

	if (!old_node) {

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, ENOMEM);

		free(old);

		free(new);

		return;

	}

	/* Lookup parent of the new file name. */

	rc = vfs_lookup_internal(newc, L_PARENT, &new_par_lr, NULL);

	if (rc != EOK) {

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, rc);

		free(old);

		free(new);

		return;

	}

	/* Check whether linking to the same file system instance. */

	if ((old_node->fs_handle != new_par_lr.triplet.fs_handle) ||

	    (old_node->dev_handle != new_par_lr.triplet.dev_handle)) {

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, EXDEV);	/* different file systems */

		free(old);

		free(new);

		return;

	}

	/* Destroy the old link for the new name. */

	vfs_node_t *new_node = NULL;

	rc = vfs_lookup_internal(newc, L_UNLINK, &new_lr, NULL);

	switch (rc) {

	case ENOENT:

		/* simply not in our way */

		break;

	case EOK:

		new_node = vfs_node_get(&new_lr);

		if (!new_node) {

			rwlock_write_unlock(&namespace_rwlock);

			ipc_answer_0(rid, ENOMEM);

			free(old);

			free(new);

			return;

		}

		futex_down(&nodes_futex);

		new_node->lnkcnt--;

		futex_up(&nodes_futex);

		break;

	default:

		rwlock_write_unlock(&namespace_rwlock);

		ipc_answer_0(rid, ENOTEMPTY);

		free(old);

		free(new);

		return;

	}

	/* Create the new link for the new name. */

	rc = vfs_lookup_internal(newc, L_LINK, NULL, NULL, old_node->index);

	if (rc != EOK) {

		rwlock_write_unlock(&namespace_rwlock);

		if (new_node)

			vfs_node_put(new_node);

		ipc_answer_0(rid, rc);

		free(old);

		free(new);

		return;

	}

	futex_down(&nodes_futex);

	old_node->lnkcnt++;

	futex_up(&nodes_futex);

	/* Destroy the link for the old name. */

	rc = vfs_lookup_internal(oldc, L_UNLINK, NULL, NULL);

	if (rc != EOK) {

		rwlock_write_unlock(&namespace_rwlock);

		vfs_node_put(old_node);

		if (new_node)

			vfs_node_put(new_node);

		ipc_answer_0(rid, rc);

		free(old);

		free(new);

		return;

	}

	futex_down(&nodes_futex);

	old_node->lnkcnt--;

	futex_up(&nodes_futex);

	rwlock_write_unlock(&namespace_rwlock);

	vfs_node_put(old_node);

	if (new_node)

		vfs_node_put(new_node);

	free(old);

	free(new);

	ipc_answer_0(rid, EOK);

}

/**

 * @}

 */