source: mainline/uspace/lib/c/generic/vfs/vfs.c@ a56cef9

/*
 * 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 libc
 * @{
 */
/** @file
 */

#include <vfs/canonify.h>
#include <vfs/vfs.h>
#include <vfs/vfs_mtab.h>
#include <vfs/vfs_sess.h>
#include <macros.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ipc/services.h>
#include <ns.h>
#include <async.h>
#include <fibril_synch.h>
#include <errno.h>
#include <assert.h>
#include <str.h>
#include <loc.h>
#include <ipc/vfs.h>
#include <ipc/loc.h>

static FIBRIL_MUTEX_INITIALIZE(vfs_mutex);
static async_sess_t *vfs_sess = NULL;

static FIBRIL_MUTEX_INITIALIZE(cwd_mutex);

static int cwd_fd = -1;
static char *cwd_path = NULL;
static size_t cwd_size = 0;

static FIBRIL_MUTEX_INITIALIZE(root_mutex);
static int root_fd = -1;

int vfs_root(void)
{
        fibril_mutex_lock(&root_mutex); 
        int r;
        if (root_fd < 0)
                r = ENOENT;
        else
                r = vfs_clone(root_fd, -1, true);
        fibril_mutex_unlock(&root_mutex);
        return r;
}

void vfs_root_set(int nroot)
{
        fibril_mutex_lock(&root_mutex);
        if (root_fd >= 0)
                close(root_fd);
        root_fd = vfs_clone(nroot, -1, true);
        fibril_mutex_unlock(&root_mutex);
}

/** Start an async exchange on the VFS session.
 *
 * @return New exchange.
 *
 */
async_exch_t *vfs_exchange_begin(void)
{
        fibril_mutex_lock(&vfs_mutex);
        
        while (vfs_sess == NULL) {
                vfs_sess = service_connect_blocking(SERVICE_VFS, INTERFACE_VFS,
                    0);
        }
        
        fibril_mutex_unlock(&vfs_mutex);
        
        return async_exchange_begin(vfs_sess);
}

/** Finish an async exchange on the VFS session.
 *
 * @param exch Exchange to be finished.
 *
 */
void vfs_exchange_end(async_exch_t *exch)
{
        async_exchange_end(exch);
}

int _vfs_walk(int parent, const char *path, int flags)
{
        async_exch_t *exch = vfs_exchange_begin();
        
        ipc_call_t answer;
        aid_t req = async_send_2(exch, VFS_IN_WALK, parent, flags, &answer);
        sysarg_t rc = async_data_write_start(exch, path, str_size(path));
        vfs_exchange_end(exch);
                
        sysarg_t rc_orig;
        async_wait_for(req, &rc_orig);

        if (rc_orig != EOK)
                return (int) rc_orig;
                
        if (rc != EOK)
                return (int) rc;
        
        return (int) IPC_GET_ARG1(answer);
}

int vfs_lookup(const char *path, int flags)
{
        size_t size;
        char *p = vfs_absolutize(path, &size);
        if (!p)
                return ENOMEM;
        int root = vfs_root();
        if (root < 0) {
                free(p);
                return ENOENT;
        }
        int rc = _vfs_walk(root, p, flags);
        close(root);
        free(p);
        return rc;
}

int _vfs_open(int fildes, int mode)
{
        async_exch_t *exch = vfs_exchange_begin();
        sysarg_t rc = async_req_2_0(exch, VFS_IN_OPEN, fildes, mode);
        vfs_exchange_end(exch);
        
        return (int) rc;
}

char *vfs_absolutize(const char *path, size_t *retlen)
{
        char *ncwd_path;
        char *ncwd_path_nc;

        fibril_mutex_lock(&cwd_mutex);
        size_t size = str_size(path);
        if (*path != '/') {
                if (cwd_path == NULL) {
                        fibril_mutex_unlock(&cwd_mutex);
                        return NULL;
                }
                ncwd_path_nc = malloc(cwd_size + 1 + size + 1);
                if (ncwd_path_nc == NULL) {
                        fibril_mutex_unlock(&cwd_mutex);
                        return NULL;
                }
                str_cpy(ncwd_path_nc, cwd_size + 1 + size + 1, cwd_path);
                ncwd_path_nc[cwd_size] = '/';
                ncwd_path_nc[cwd_size + 1] = '\0';
        } else {
                ncwd_path_nc = malloc(size + 1);
                if (ncwd_path_nc == NULL) {
                        fibril_mutex_unlock(&cwd_mutex);
                        return NULL;
                }
                ncwd_path_nc[0] = '\0';
        }
        str_append(ncwd_path_nc, cwd_size + 1 + size + 1, path);
        ncwd_path = canonify(ncwd_path_nc, retlen);
        if (ncwd_path == NULL) {
                fibril_mutex_unlock(&cwd_mutex);
                free(ncwd_path_nc);
                return NULL;
        }
        /*
         * We need to clone ncwd_path because canonify() works in-place and thus
         * the address in ncwd_path need not be the same as ncwd_path_nc, even
         * though they both point into the same dynamically allocated buffer.
         */
        ncwd_path = str_dup(ncwd_path);
        free(ncwd_path_nc);
        if (ncwd_path == NULL) {
                fibril_mutex_unlock(&cwd_mutex);
                return NULL;
        }
        fibril_mutex_unlock(&cwd_mutex);
        return ncwd_path;
}

int vfs_mount(int mp, const char *fs_name, service_id_t serv, const char *opts,
    unsigned int flags, unsigned int instance, int *mountedfd)
{
        sysarg_t rc, rc1;
        
        if (!mountedfd)
                flags |= VFS_MOUNT_NO_REF;
        if (mp < 0)
                flags |= VFS_MOUNT_CONNECT_ONLY;
        
        ipc_call_t answer;
        async_exch_t *exch = vfs_exchange_begin();
        aid_t req = async_send_4(exch, VFS_IN_MOUNT, mp, serv, flags, instance,
            &answer);

        rc1 = async_data_write_start(exch, (void *) opts, str_size(opts));
        if (rc1 == EOK) {
                rc1 = async_data_write_start(exch, (void *) fs_name,
                    str_size(fs_name));
        }

        vfs_exchange_end(exch);

        async_wait_for(req, &rc);

        if (mountedfd)
                *mountedfd = (int) IPC_GET_ARG1(answer);
        
        if (rc != EOK)
                return rc;
        return rc1;
}

int vfs_unmount(int mp)
{
        async_exch_t *exch = vfs_exchange_begin();
        int rc = async_req_1_0(exch, VFS_IN_UNMOUNT, mp);
        vfs_exchange_end(exch);
        return rc;
}

int mount(const char *fs_name, const char *mp, const char *fqsn,
    const char *opts, unsigned int flags, unsigned int instance)
{
        int null_id = -1;
        char null[LOC_NAME_MAXLEN];
        
        if (str_cmp(fqsn, "") == 0) {
                /*
                 * No device specified, create a fresh null/%d device instead.
                */
                null_id = loc_null_create();
                
                if (null_id == -1)
                        return ENOMEM;
                
                snprintf(null, LOC_NAME_MAXLEN, "null/%d", null_id);
                fqsn = null;
        }
        
        if (flags & IPC_FLAG_BLOCKING)
                flags = VFS_MOUNT_BLOCKING;
        else
                flags = 0;
        
        service_id_t service_id;
        int res = loc_service_get_id(fqsn, &service_id, flags);
        if (res != EOK) {
                if (null_id != -1)
                        loc_null_destroy(null_id);
                
                return res;
        }
        
        size_t mpa_size;
        char *mpa = vfs_absolutize(mp, &mpa_size);
        if (mpa == NULL) {
                if (null_id != -1)
                        loc_null_destroy(null_id);
                
                return ENOMEM;
        }
        
        fibril_mutex_lock(&root_mutex);
        
        int rc;
        
        if (str_cmp(mpa, "/") == 0) {
                /* Mounting root. */
                
                if (root_fd >= 0) {
                        fibril_mutex_unlock(&root_mutex);
                        if (null_id != -1)
                                loc_null_destroy(null_id);
                        return EBUSY;
                }
                
                int root;
                rc = vfs_mount(-1, fs_name, service_id, opts, flags, instance,
                    &root);
                if (rc == EOK)
                        root_fd = root;
        } else {
                if (root_fd < 0) {
                        fibril_mutex_unlock(&root_mutex);
                        if (null_id != -1)
                                loc_null_destroy(null_id);
                        return EINVAL;
                }
                
                int mpfd = _vfs_walk(root_fd, mpa, WALK_DIRECTORY);
                if (mpfd >= 0) {
                        rc = vfs_mount(mpfd, fs_name, service_id, opts, flags,
                            instance, NULL);
                        close(mpfd);
                } else {
                        rc = mpfd;
                }
        }
        
        fibril_mutex_unlock(&root_mutex);
        
        if ((rc != EOK) && (null_id != -1))
                loc_null_destroy(null_id);
        
        return (int) rc;
}

int unmount(const char *mpp)
{
        int mp = vfs_lookup(mpp, WALK_MOUNT_POINT | WALK_DIRECTORY);
        if (mp < 0)
                return mp;
        
        int rc = vfs_unmount(mp);
        close(mp);
        return rc;
}

static int walk_flags(int oflags)
{
        int flags = 0;
        if (oflags & O_CREAT) {
                if (oflags & O_EXCL)
                        flags |= WALK_MUST_CREATE;
                else
                        flags |= WALK_MAY_CREATE;
        }
        return flags;
}

/** Open file.
 *
 * @param path File path
 * @param oflag O_xxx flags
 * @param mode File mode (only with O_CREAT)
 *
 * @return Nonnegative file descriptor on success. On error -1 is returned
 *         and errno is set.
 */
int open(const char *path, int oflag, ...)
{
        if (((oflag & (O_RDONLY | O_WRONLY | O_RDWR)) == 0) ||
            ((oflag & (O_RDONLY | O_WRONLY)) == (O_RDONLY | O_WRONLY)) ||
            ((oflag & (O_RDONLY | O_RDWR)) == (O_RDONLY | O_RDWR)) ||
            ((oflag & (O_WRONLY | O_RDWR)) == (O_WRONLY | O_RDWR))) {
                errno = EINVAL;
                return -1;
        }
        
        int fd = vfs_lookup(path, walk_flags(oflag) | WALK_REGULAR);
        if (fd < 0) {
                errno = fd;
                return -1;
        }
        
        int mode =
            ((oflag & O_RDWR) ? MODE_READ | MODE_WRITE : 0) |
            ((oflag & O_RDONLY) ? MODE_READ : 0) |
            ((oflag & O_WRONLY) ? MODE_WRITE : 0) |
            ((oflag & O_APPEND) ? MODE_APPEND : 0);
        
        int rc = _vfs_open(fd, mode); 
        if (rc < 0) {
                close(fd);
                errno = rc;
                return -1;
        }
        
        if (oflag & O_TRUNC) {
                assert(oflag & O_WRONLY || oflag & O_RDWR);
                assert(!(oflag & O_APPEND));
                
                (void) vfs_resize(fd, 0);
        }

        return fd;
}

/** Close file.
 *
 * @param fildes File descriptor
 * @return Zero on success. On error -1 is returned and errno is set.
 */
int close(int fildes)
{
        sysarg_t rc;
        
        async_exch_t *exch = vfs_exchange_begin();
        rc = async_req_1_0(exch, VFS_IN_CLOSE, fildes);
        vfs_exchange_end(exch);
        
        if (rc != EOK) {
                errno = rc;
                return -1;
        }
        
        return 0;
}

/** Read bytes from file.
 *
 * Read up to @a nbyte bytes from file. The actual number of bytes read
 * may be lower, but greater than zero if there are any bytes available.
 * If there are no bytes available for reading, then the function will
 * return success with zero bytes read.
 *
 * @param fildes File descriptor
 * @param pos Position to read from
 * @param buf Buffer
 * @param nbyte Maximum number of bytes to read
 * @param nread Place to store actual number of bytes read (0 or more)
 *
 * @return EOK on success, non-zero error code on error.
 */
static int _read_short(int fildes, aoff64_t pos, void *buf, size_t nbyte,
    ssize_t *nread)
{
        sysarg_t rc;
        ipc_call_t answer;
        aid_t req;
        
        if (nbyte > DATA_XFER_LIMIT)
                nbyte = DATA_XFER_LIMIT;
        
        async_exch_t *exch = vfs_exchange_begin();
        
        req = async_send_3(exch, VFS_IN_READ, fildes, LOWER32(pos),
            UPPER32(pos), &answer);
        rc = async_data_read_start(exch, (void *) buf, nbyte);

        vfs_exchange_end(exch);
        
        if (rc == EOK)
                async_wait_for(req, &rc);
        else
                async_forget(req);
        
        if (rc != EOK)
                return rc;
        
        *nread = (ssize_t) IPC_GET_ARG1(answer);
        return EOK;
}

/** Write bytes to file.
 *
 * Write up to @a nbyte bytes from file. The actual number of bytes written
 * may be lower, but greater than zero.
 *
 * @param fildes File descriptor
 * @param pos Position to write to
 * @param buf Buffer
 * @param nbyte Maximum number of bytes to write
 * @param nread Place to store actual number of bytes written (0 or more)
 *
 * @return EOK on success, non-zero error code on error.
 */
static int _write_short(int fildes, aoff64_t pos, const void *buf, size_t nbyte,
    ssize_t *nwritten)
{
        sysarg_t rc;
        ipc_call_t answer;
        aid_t req;
        
        if (nbyte > DATA_XFER_LIMIT)
                nbyte = DATA_XFER_LIMIT;
        
        async_exch_t *exch = vfs_exchange_begin();
        
        req = async_send_3(exch, VFS_IN_WRITE, fildes, LOWER32(pos),
            UPPER32(pos), &answer);
        rc = async_data_write_start(exch, (void *) buf, nbyte);
        
        vfs_exchange_end(exch);
        
        if (rc == EOK)
                async_wait_for(req, &rc);
        else
                async_forget(req);

        if (rc != EOK)
                return rc;
        
        *nwritten = (ssize_t) IPC_GET_ARG1(answer);
        return EOK;
}

/** Read data.
 *
 * Read up to @a nbytes bytes from file if available. This function always reads
 * all the available bytes up to @a nbytes.
 *
 * @param fildes        File descriptor
 * @param pos           Pointer to position to read from 
 * @param buf           Buffer, @a nbytes bytes long
 * @param nbytes        Number of bytes to read
 *
 * @return              On success, nonnegative number of bytes read.
 *                      On failure, -1 and sets errno.
 */
ssize_t read(int fildes, aoff64_t *pos, void *buf, size_t nbyte)
{
        ssize_t cnt = 0;
        size_t nread = 0;
        uint8_t *bp = (uint8_t *) buf;
        int rc;
        
        do {
                bp += cnt;
                nread += cnt;
                *pos += cnt;
                rc = _read_short(fildes, *pos, bp, nbyte - nread, &cnt);
        } while (rc == EOK && cnt > 0 && (nbyte - nread - cnt) > 0);
        
        if (rc != EOK) {
                errno = rc;
                return -1;
        }
        
        *pos += cnt;
        return nread + cnt;
}

/** Write data.
 *
 * This function fails if it cannot write exactly @a len bytes to the file.
 *
 * @param fildes        File descriptor
 * @param pos           Pointer to position to write to
 * @param buf           Data, @a nbytes bytes long
 * @param nbytes        Number of bytes to write
 *
 * @return              On success, nonnegative number of bytes written.
 *                      On failure, -1 and sets errno.
 */
ssize_t write(int fildes, aoff64_t *pos, const void *buf, size_t nbyte)
{
        ssize_t cnt = 0;
        ssize_t nwritten = 0;
        const uint8_t *bp = (uint8_t *) buf;
        int rc;

        do {
                bp += cnt;
                nwritten += cnt;
                *pos += cnt;
                rc = _write_short(fildes, *pos, bp, nbyte - nwritten, &cnt);
        } while (rc == EOK && ((ssize_t )nbyte - nwritten - cnt) > 0);

        if (rc != EOK) {
                errno = rc;
                return -1;
        }

        *pos += cnt;
        return nbyte;
}

/** Synchronize file.
 *
 * @param fildes File descriptor
 * @return EOK on success or a negative error code otherwise.
 */
int vfs_sync(int file)
{
        async_exch_t *exch = vfs_exchange_begin();
        sysarg_t rc = async_req_1_0(exch, VFS_IN_SYNC, file);
        vfs_exchange_end(exch);
        
        return rc;
}

/** Truncate file to a specified length.
 *
 * Truncate file so that its size is exactly @a length
 *
 * @param fildes File descriptor
 * @param length Length
 *
 * @return EOK on success or a negative erroc code otherwise.
 */
int vfs_resize(int file, aoff64_t length)
{
        sysarg_t rc;
        
        async_exch_t *exch = vfs_exchange_begin();
        rc = async_req_3_0(exch, VFS_IN_RESIZE, file, LOWER32(length),
            UPPER32(length));
        vfs_exchange_end(exch);
        
        return rc;
}

/** Get file status.
 *
 * @param file File descriptor
 * @param stat Place to store file information
 *
 * @return EOK on success or a negative error code otherwise.
 */
int vfs_stat(int file, struct stat *stat)
{
        sysarg_t rc;
        aid_t req;
        
        async_exch_t *exch = vfs_exchange_begin();
        
        req = async_send_1(exch, VFS_IN_STAT, file, NULL);
        rc = async_data_read_start(exch, (void *) stat, sizeof(struct stat));
        if (rc != EOK) {
                vfs_exchange_end(exch);
                
                sysarg_t rc_orig;
                async_wait_for(req, &rc_orig);
                
                if (rc_orig != EOK)
                        rc = rc_orig;
                
                return rc;
        }
        
        vfs_exchange_end(exch);
        async_wait_for(req, &rc);
        
        return rc;
}

/** Get file status.
 *
 * @param path Path to file
 * @param stat Place to store file information
 *
 * @return EOK on success or a negative error code otherwise.
 */
int vfs_stat_path(const char *path, struct stat *stat)
{
        int file = vfs_lookup(path, 0);
        if (file < 0)
                return file;
        
        int rc = vfs_stat(file, stat);

        close(file);

        return rc;
}

/** Open directory.
 *
 * @param dirname Directory pathname
 *
 * @return Non-NULL pointer on success. On error returns @c NULL and sets errno.
 */
DIR *opendir(const char *dirname)
{
        DIR *dirp = malloc(sizeof(DIR));
        if (!dirp) {
                errno = ENOMEM;
                return NULL;
        }
        
        int fd = vfs_lookup(dirname, WALK_DIRECTORY);
        if (fd < 0) {
                free(dirp);
                errno = fd;
                return NULL;
        }
        
        int rc = _vfs_open(fd, MODE_READ);
        if (rc < 0) {
                free(dirp);
                close(fd);
                errno = rc;
                return NULL;
        }
        
        dirp->fd = fd;
        dirp->pos = 0;
        return dirp;
}

/** Read directory entry.
 *
 * @param dirp Open directory
 * @return Non-NULL pointer to directory entry on success. On error returns
 *         @c NULL and sets errno.
 */
struct dirent *readdir(DIR *dirp)
{
        int rc;
        ssize_t len = 0;
        
        rc = _read_short(dirp->fd, dirp->pos, &dirp->res.d_name[0],
            NAME_MAX + 1, &len);
        if (rc != EOK) {
                errno = rc;
                return NULL;
        }
        
        dirp->pos += len;
        
        return &dirp->res;
}

/** Rewind directory position to the beginning.
 *
 * @param dirp Open directory
 */
void rewinddir(DIR *dirp)
{
        dirp->pos = 0;
}

/** Close directory.
 *
 * @param dirp Open directory
 * @return 0 on success. On error returns -1 and sets errno.
 */
int closedir(DIR *dirp)
{
        int rc;
        
        rc = close(dirp->fd);
        free(dirp);

        /* On error errno was set by close() */
        return rc;
}

/** Create directory.
 *
 * @param path Path
 * @param mode File mode
 * @return 0 on success. On error returns -1 and sets errno.
 */
int mkdir(const char *path, mode_t mode)
{
        int fd = vfs_lookup(path, WALK_MUST_CREATE | WALK_DIRECTORY);
        if (fd < 0) {
                errno = fd;
                return -1;
        }
        
        return close(fd);
}

int vfs_unlink(int parent, const char *child, int expect)
{
        sysarg_t rc;
        aid_t req;
        
        async_exch_t *exch = vfs_exchange_begin();
        
        req = async_send_2(exch, VFS_IN_UNLINK, parent, expect, NULL);
        rc = async_data_write_start(exch, child, str_size(child));
        
        vfs_exchange_end(exch);
        
        sysarg_t rc_orig;
        async_wait_for(req, &rc_orig);
        
        if (rc_orig != EOK)
                return (int) rc_orig;
        return rc;
}

/** Unlink file or directory.
 *
 * @param path Path
 * @return EOk on success or a negative error code otherwise
 */
int vfs_unlink_path(const char *path)
{
        size_t pa_size;
        char *pa = vfs_absolutize(path, &pa_size);
        if (!pa)
                return ENOMEM;

        int parent;
        int expect = vfs_lookup(path, 0);
        if (expect < 0) {
                free(pa);
                return expect;
        }

        char *slash = str_rchr(pa, L'/');
        if (slash != pa) {
                *slash = '\0';
                parent = vfs_lookup(pa, 0);
                *slash = '/';
        } else {
                parent = vfs_root();
        }

        if (parent < 0) {
                free(pa);
                close(expect);
                return parent;
        }

        int rc = vfs_unlink(parent, slash, expect);
        
        free(pa);
        close(parent);
        close(expect);
        return rc;
}

/** Rename directory entry.
 *
 * @param old Old name
 * @param new New name
 *
 * @return 0 on success. On error returns -1 and sets errno.
 */
int rename(const char *old, const char *new)
{
        sysarg_t rc;
        sysarg_t rc_orig;
        aid_t req;
        
        size_t olda_size;
        char *olda = vfs_absolutize(old, &olda_size);
        if (olda == NULL) {
                errno = ENOMEM;
                return -1;
        }

        size_t newa_size;
        char *newa = vfs_absolutize(new, &newa_size);
        if (newa == NULL) {
                free(olda);
                errno = ENOMEM;
                return -1;
        }
        
        async_exch_t *exch = vfs_exchange_begin();
        int root = vfs_root();
        if (root < 0) {
                free(olda);
                free(newa);
                errno = ENOENT;
                return -1;
        }
        
        req = async_send_1(exch, VFS_IN_RENAME, root, NULL);
        rc = async_data_write_start(exch, olda, olda_size);
        if (rc != EOK) {
                vfs_exchange_end(exch);
                free(olda);
                free(newa);
                close(root);
                async_wait_for(req, &rc_orig);
                if (rc_orig != EOK)
                        rc = rc_orig;
                if (rc != EOK) {
                        errno = rc;
                        return -1;
                }
                return 0;
        }
        rc = async_data_write_start(exch, newa, newa_size);
        if (rc != EOK) {
                vfs_exchange_end(exch);
                free(olda);
                free(newa);
                close(root);
                async_wait_for(req, &rc_orig);
                if (rc_orig != EOK)
                        rc = rc_orig;
                if (rc != EOK) {
                        errno = rc;
                        return -1;
                }
                return 0;
        }
        vfs_exchange_end(exch);
        free(olda);
        free(newa);
        close(root);
        async_wait_for(req, &rc);

        if (rc != EOK) {
                errno = rc;
                return -1;
        }

        return 0;
}

/** Change working directory.
 *
 * @param path Path
 * @return 0 on success. On error returns -1 and sets errno.
 */
int chdir(const char *path)
{
        size_t abs_size;
        char *abs = vfs_absolutize(path, &abs_size);
        if (!abs) {
                errno = ENOMEM;
                return -1;
        }
        
        int fd = vfs_lookup(abs, WALK_DIRECTORY);
        if (fd < 0) {
                free(abs);
                errno = fd;
                return -1;
        }
        
        fibril_mutex_lock(&cwd_mutex);
        
        if (cwd_fd >= 0)
                close(cwd_fd);
        
        if (cwd_path)
                free(cwd_path);
        
        cwd_fd = fd;
        cwd_path = abs;
        cwd_size = abs_size;
        
        fibril_mutex_unlock(&cwd_mutex);
        return 0;
}

/** Get current working directory path.
 *
 * @param buf Buffer
 * @param size Size of @a buf
 * @return On success returns @a buf. On failure returns @c NULL and sets errno.
 */
char *getcwd(char *buf, size_t size)
{
        if (size == 0) {
                errno = EINVAL;
                return NULL;
        }
        
        fibril_mutex_lock(&cwd_mutex);
        
        if ((cwd_size == 0) || (size < cwd_size + 1)) {
                fibril_mutex_unlock(&cwd_mutex);
                errno = ERANGE;
                return NULL;
        }
        
        str_cpy(buf, size, cwd_path);
        fibril_mutex_unlock(&cwd_mutex);
        
        return buf;
}

/** Open session to service represented by a special file.
 *
 * Given that the file referred to by @a fildes represents a service,
 * open a session to that service.
 *
 * @param fildes File descriptor
 * @param iface Interface to connect to (XXX Should be automatic)
 * @return On success returns session pointer. On error returns @c NULL.
 */
async_sess_t *vfs_fd_session(int file, iface_t iface)
{
        struct stat stat;
        int rc = vfs_stat(file, &stat);
        if (rc != 0)
                return NULL;
        
        if (stat.service == 0)
                return NULL;
        
        return loc_service_connect(stat.service, iface, 0);
}

static void process_mp(const char *path, struct stat *stat, list_t *mtab_list)
{
        mtab_ent_t *ent;

        ent = (mtab_ent_t *) malloc(sizeof(mtab_ent_t));
        if (!ent)
                return;

        link_initialize(&ent->link);
        str_cpy(ent->mp, sizeof(ent->mp), path);
        ent->service_id = stat->service_id;

        struct statfs stfs;
        if (vfs_statfs_path(path, &stfs) == EOK)
                str_cpy(ent->fs_name, sizeof(ent->fs_name), stfs.fs_name);
        else
                str_cpy(ent->fs_name, sizeof(ent->fs_name), "?");
        
        list_append(&ent->link, mtab_list);
}

static int vfs_get_mtab_visit(const char *path, list_t *mtab_list,
    fs_handle_t fs_handle, service_id_t service_id)
{
        DIR *dir;
        struct dirent *dirent;

        dir = opendir(path);
        if (!dir)
                return ENOENT;

        while ((dirent = readdir(dir)) != NULL) {
                char *child;
                struct stat st;
                int rc;

                rc = asprintf(&child, "%s/%s", path, dirent->d_name);
                if (rc < 0) {
                        closedir(dir);
                        return rc;
                }

                char *pa = vfs_absolutize(child, NULL);
                if (!pa) {
                        free(child);
                        closedir(dir);
                        return ENOMEM;
                }

                free(child);
                child = pa;

                rc = vfs_stat_path(child, &st);
                if (rc != 0) {
                        free(child);
                        closedir(dir);
                        return rc;
                }

                if (st.fs_handle != fs_handle || st.service_id != service_id) {
                        /*
                         * We have discovered a mountpoint.
                         */
                        process_mp(child, &st, mtab_list);
                }

                if (st.is_directory) {
                        (void) vfs_get_mtab_visit(child, mtab_list,
                            st.fs_handle, st.service_id);
                }

                free(child);
        }

        closedir(dir);
        return EOK;
}

int vfs_get_mtab_list(list_t *mtab_list)
{
        struct stat st;

        int rc = vfs_stat_path("/", &st);
        if (rc != 0)
                return rc;

        process_mp("/", &st, mtab_list);

        return vfs_get_mtab_visit("/", mtab_list, st.fs_handle, st.service_id);
}

/** Get filesystem statistics.
 *
 * @param file File located on the queried file system
 * @param st Buffer for storing information
 * @return EOK on success or a negative error code otherwise.
 */
int vfs_statfs(int file, struct statfs *st)
{
        sysarg_t rc, ret;
        aid_t req;

        async_exch_t *exch = vfs_exchange_begin();

        req = async_send_1(exch, VFS_IN_STATFS, file, NULL);
        rc = async_data_read_start(exch, (void *) st, sizeof(*st));

        vfs_exchange_end(exch);
        async_wait_for(req, &ret);

        rc = (ret != EOK ? ret : rc);

        return rc;
}
/** Get filesystem statistics.
 *
 * @param path Mount point path
 * @param st Buffer for storing information
 * @return EOK on success or a negative error code otherwise.
 */
int vfs_statfs_path(const char *path, struct statfs *st)
{
        int file = vfs_lookup(path, 0);
        if (file < 0)
                return file;
        
        int rc = vfs_statfs(file, st);

        close(file);

        return rc; 
}

int vfs_pass_handle(async_exch_t *vfs_exch, int file, async_exch_t *exch)
{
        return async_state_change_start(exch, VFS_PASS_HANDLE, (sysarg_t) file,
            0, vfs_exch);
}

int vfs_receive_handle(bool high_descriptor)
{
        ipc_callid_t callid;
        if (!async_state_change_receive(&callid, NULL, NULL, NULL)) {
                async_answer_0(callid, EINVAL);
                return EINVAL;
        }

        async_exch_t *vfs_exch = vfs_exchange_begin();

        async_state_change_finalize(callid, vfs_exch);

        sysarg_t ret;
        sysarg_t rc = async_req_1_1(vfs_exch, VFS_IN_WAIT_HANDLE,
            high_descriptor, &ret);

        async_exchange_end(vfs_exch);

        if (rc != EOK)
                return rc;
        return ret;
}

int vfs_clone(int file_from, int file_to, bool high_descriptor)
{
        async_exch_t *vfs_exch = vfs_exchange_begin();
        int rc = async_req_3_0(vfs_exch, VFS_IN_CLONE, (sysarg_t) file_from,
            (sysarg_t) file_to, (sysarg_t) high_descriptor);
        vfs_exchange_end(vfs_exch);
        return rc;
}

/** @}
 */