[wimlib] / src / mount_image.c

/*
 * mount_image.c
 *
 * This file implements mounting of WIM files using FUSE, which stands for
 * Filesystem in Userspace.  FUSE allows a filesystem to be implemented in a
 * userspace process by implementing the filesystem primitives--- read(),
 * write(), readdir(), etc.
 */

/*
 * Copyright (C) 2012, 2013, 2014 Eric Biggers
 *
 * This file is part of wimlib, a library for working with WIM files.
 *
 * wimlib is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 3 of the License, or (at your option)
 * any later version.
 *
 * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with wimlib; if not, see http://www.gnu.org/licenses/.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "wimlib.h"
#include "wimlib/error.h"

#ifdef WITH_FUSE

#ifdef __WIN32__
#  error "FUSE mount not supported on Win32!  Please configure --without-fuse"
#endif

#include "wimlib/encoding.h"
#include "wimlib/file_io.h"
#include "wimlib/dentry.h"
#include "wimlib/inode.h"
#include "wimlib/lookup_table.h"
#include "wimlib/metadata.h"
#include "wimlib/paths.h"
#include "wimlib/reparse.h"
#include "wimlib/resource.h"
#include "wimlib/timestamp.h"
#include "wimlib/version.h"
#include "wimlib/write.h"
#include "wimlib/xml.h"

#include <errno.h>
#include <ftw.h>
#include <limits.h>
#include <mqueue.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utime.h>

#define FUSE_USE_VERSION 26
#include <fuse.h>

#ifdef ENABLE_XATTR
#include <attr/xattr.h>
#endif

#define MSG_VERSION_TOO_HIGH    -1
#define MSG_BREAK_LOOP          -2

/* File descriptor to a file open on the WIM filesystem. */
struct wimfs_fd {
        struct wim_inode *f_inode;
        struct wim_lookup_table_entry *f_lte;
        struct filedes staging_fd;
        u16 idx;
        u32 stream_id;
};

struct wimfs_context {
        /* The WIMStruct for the mounted WIM. */
        WIMStruct *wim;

        /* Name of the staging directory for a read-write mount.  Whenever a new file is
         * created, it is done so in the staging directory.  Furthermore, whenever a
         * file in the WIM is modified, it is extracted to the staging directory.  If
         * changes are commited when the WIM is unmounted, the file resources are merged
         * in from the staging directory when writing the new WIM. */
        char *staging_dir_name;
        size_t staging_dir_name_len;

        /* Flags passed to wimlib_mount(). */
        int mount_flags;

        /* Default flags to use when looking up a WIM dentry (depends on whether
         * the Windows interface to alternate data streams is being used or
         * not). */
        int default_lookup_flags;

        /* Next inode number to be assigned.  Note: I didn't bother with a
         * bitmap of free inode numbers since this isn't even a "real"
         * filesystem anyway. */
        u64 next_ino;

        /* List of inodes in the mounted image */
        struct list_head *image_inode_list;

        /* Original list of streams in the mounted image, linked by
         * mount_orig_stream_list.  */
        struct list_head orig_stream_list;

        /* Name and message queue descriptors for message queues between the
         * filesystem daemon process and the unmount process.  These are used
         * when the filesystem is unmounted and the process running
         * wimlib_unmount_image() needs to communicate with the filesystem
         * daemon running fuse_main() (i.e. the process created by a call to
         * wimlib_mount_image().  */
        char *unmount_to_daemon_mq_name;
        char *daemon_to_unmount_mq_name;
        mqd_t unmount_to_daemon_mq;
        mqd_t daemon_to_unmount_mq;

        uid_t default_uid;
        gid_t default_gid;

        int status;
        bool have_status;
};

static void
init_wimfs_context(struct wimfs_context *ctx)
{
        memset(ctx, 0, sizeof(*ctx));
        ctx->unmount_to_daemon_mq = (mqd_t)-1;
        ctx->daemon_to_unmount_mq = (mqd_t)-1;
}

#define WIMFS_CTX(fuse_ctx) ((struct wimfs_context*)(fuse_ctx)->private_data)

static inline struct wimfs_context *
wimfs_get_context(void)
{
        return WIMFS_CTX(fuse_get_context());
}

static inline WIMStruct *
wimfs_get_WIMStruct(void)
{
        return wimfs_get_context()->wim;
}

static inline int
get_lookup_flags(const struct wimfs_context *ctx)
{
        return ctx->default_lookup_flags;
}

/* Returns nonzero if write permission is requested on the file open flags */
static inline int
flags_writable(int open_flags)
{
        int accmode = (open_flags & O_ACCMODE);
        return (accmode == O_RDWR || accmode == O_WRONLY);
}

/*
 * Allocate a file descriptor for a stream.
 *
 * @inode:      inode containing the stream we're opening
 * @stream_id:  ID of the stream we're opening
 * @lte:        Lookup table entry for the stream (may be NULL)
 * @fd_ret:     Return the allocated file descriptor if successful.
 *
 * Return 0 iff successful or negative error code if unsuccessful.
 */
static int
alloc_wimfs_fd(struct wim_inode *inode,
               u32 stream_id,
               struct wim_lookup_table_entry *lte,
               struct wimfs_fd **fd_ret)
{
        static const u16 fds_per_alloc = 8;
        static const u16 max_fds = 0xffff;

        DEBUG("Allocating fd for stream ID %u from inode %#"PRIx64" "
              "(open = %u, allocated = %u)",
              stream_id, inode->i_ino, inode->i_num_opened_fds,
              inode->i_num_allocated_fds);

        if (inode->i_num_opened_fds == inode->i_num_allocated_fds) {
                struct wimfs_fd **fds;
                u16 num_new_fds;

                if (inode->i_num_allocated_fds == max_fds)
                        return -EMFILE;

                num_new_fds = min(fds_per_alloc,
                                  max_fds - inode->i_num_allocated_fds);

                fds = REALLOC(inode->i_fds,
                              (inode->i_num_allocated_fds + num_new_fds) *
                                sizeof(inode->i_fds[0]));
                if (!fds)
                        return -ENOMEM;

                memset(&fds[inode->i_num_allocated_fds], 0,
                       num_new_fds * sizeof(fds[0]));
                inode->i_fds = fds;
                inode->i_num_allocated_fds += num_new_fds;
        }
        for (u16 i = 0; ; i++) {
                if (!inode->i_fds[i]) {
                        struct wimfs_fd *fd = CALLOC(1, sizeof(*fd));
                        if (!fd)
                                return -ENOMEM;

                        fd->f_inode     = inode;
                        fd->f_lte       = lte;
                        filedes_invalidate(&fd->staging_fd);
                        fd->idx         = i;
                        fd->stream_id   = stream_id;
                        *fd_ret         = fd;
                        inode->i_fds[i] = fd;
                        inode->i_num_opened_fds++;
                        if (lte)
                                lte->num_opened_fds++;
                        DEBUG("Allocated fd (idx = %u)", fd->idx);
                        return 0;
                }
        }
}

static void
inode_put_fd(struct wim_inode *inode, struct wimfs_fd *fd)
{
        wimlib_assert(inode != NULL);
        wimlib_assert(fd->f_inode == inode);
        wimlib_assert(inode->i_num_opened_fds != 0);
        wimlib_assert(fd->idx < inode->i_num_allocated_fds);
        wimlib_assert(inode->i_fds[fd->idx] == fd);

        inode->i_fds[fd->idx] = NULL;
        FREE(fd);
        if (--inode->i_num_opened_fds == 0) {
                FREE(inode->i_fds);
                inode->i_fds = NULL;
                inode->i_num_allocated_fds = 0;
                if (inode->i_nlink == 0)
                        free_inode(inode);
        }
}

static int
lte_put_fd(struct wim_lookup_table_entry *lte, struct wimfs_fd *fd)
{
        wimlib_assert(fd->f_lte == lte);

        if (!lte) /* Empty stream with no lookup table entry */
                return 0;

        /* Close staging file descriptor if needed. */

        if (lte->resource_location == RESOURCE_IN_STAGING_FILE
             && filedes_valid(&fd->staging_fd))
        {
                if (filedes_close(&fd->staging_fd)) {
                        ERROR_WITH_ERRNO("Failed to close staging file");
                        return -errno;
                }
        }
        lte_decrement_num_opened_fds(lte);
        return 0;
}

/* Close a file descriptor. */
static int
close_wimfs_fd(struct wimfs_fd *fd)
{
        int ret;
        DEBUG("Closing fd (ino = %#"PRIx64", opened = %u, allocated = %u)",
              fd->f_inode->i_ino, fd->f_inode->i_num_opened_fds,
              fd->f_inode->i_num_allocated_fds);
        ret = lte_put_fd(fd->f_lte, fd);
        if (ret)
                return ret;

        inode_put_fd(fd->f_inode, fd);
        return 0;
}

static mode_t
fuse_mask_mode(mode_t mode, struct fuse_context *fuse_ctx)
{
#if FUSE_MAJOR_VERSION > 2 || (FUSE_MAJOR_VERSION == 2 && FUSE_MINOR_VERSION >= 8)
        mode &= ~fuse_ctx->umask;
#endif
        return mode;
}

/*
 * Add a new dentry with a new inode to a WIM image.
 *
 * Returns 0 on success, or negative error number on failure.
 */
static int
create_dentry(struct fuse_context *fuse_ctx, const char *path,
              mode_t mode, int attributes, struct wim_dentry **dentry_ret)
{
        struct wim_dentry *parent;
        struct wim_dentry *new;
        const char *basename;
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);
        int ret;

        parent = get_parent_dentry(wimfs_ctx->wim, path, WIMLIB_CASE_SENSITIVE);
        if (!parent)
                return -errno;

        if (!dentry_is_directory(parent))
                return -ENOTDIR;

        basename = path_basename(path);
        if (get_dentry_child_with_name(parent, basename, WIMLIB_CASE_SENSITIVE))
                return -EEXIST;

        ret = new_dentry_with_inode(basename, &new);
        if (ret)
                return -ENOMEM;

        new->d_inode->i_resolved = 1;
        new->d_inode->i_ino = wimfs_ctx->next_ino++;
        new->d_inode->i_attributes = attributes;

        if (wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA) {
                if (inode_set_unix_data(new->d_inode,
                                        fuse_ctx->uid,
                                        fuse_ctx->gid,
                                        fuse_mask_mode(mode, fuse_ctx),
                                        wimfs_ctx->wim->lookup_table,
                                        UNIX_DATA_ALL | UNIX_DATA_CREATE))
                {
                        free_dentry(new);
                        return -ENOMEM;
                }
        }
        dentry_add_child(parent, new);
        list_add_tail(&new->d_inode->i_list, wimfs_ctx->image_inode_list);
        if (dentry_ret)
                *dentry_ret = new;
        return 0;
}

static struct wim_inode *
wim_pathname_to_inode(WIMStruct *wim, const tchar *path)
{
        struct wim_dentry *dentry;
        dentry = get_dentry(wim, path, WIMLIB_CASE_SENSITIVE);
        if (dentry)
                return dentry->d_inode;
        else
                return NULL;
}

/* Remove a dentry from a mounted WIM image; i.e. remove an alias for the
 * corresponding inode.
 *
 * If there are no remaining references to the inode either through dentries or
 * open file descriptors, the inode is freed.  Otherwise, the inode is not
 * removed, but the dentry is unlinked and freed.
 *
 * Either way, all lookup table entries referenced by the inode have their
 * reference count decremented.  If a lookup table entry has no open file
 * descriptors and no references remaining, it is freed, and the corresponding
 * staging file is unlinked.
 */
static void
remove_dentry(struct wim_dentry *dentry,
              struct wim_lookup_table *lookup_table)
{
        struct wim_inode *inode = dentry->d_inode;
        struct wim_lookup_table_entry *lte;
        unsigned i;

        for (i = 0; i <= inode->i_num_ads; i++) {
                lte = inode_stream_lte(inode, i, lookup_table);
                if (lte)
                        lte_decrement_refcnt(lte, lookup_table);
        }
        unlink_dentry(dentry);
        free_dentry(dentry);
}

static mode_t
inode_default_unix_mode(const struct wim_inode *inode)
{
        if (inode_is_symlink(inode))
                return S_IFLNK | 0777;
        else if (inode_is_directory(inode))
                return S_IFDIR | 0777;
        else
                return S_IFREG | 0777;
}

/* Transfers file attributes from a struct wim_inode to a `stat' buffer.
 *
 * The lookup table entry tells us which stream in the inode we are statting.
 * For a named data stream, everything returned is the same as the unnamed data
 * stream except possibly the size and block count. */
static int
inode_to_stbuf(const struct wim_inode *inode,
               const struct wim_lookup_table_entry *lte,
               struct stat *stbuf)
{
        const struct wimfs_context *ctx = wimfs_get_context();

        memset(stbuf, 0, sizeof(struct stat));
        stbuf->st_mode = inode_default_unix_mode(inode);
        stbuf->st_uid = ctx->default_uid;
        stbuf->st_gid = ctx->default_gid;
        if (ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA) {
                struct wimlib_unix_data unix_data;
                if (inode_get_unix_data(inode, &unix_data, NULL) == 0) {
                        stbuf->st_uid = unix_data.uid;
                        stbuf->st_gid = unix_data.gid;
                        stbuf->st_mode = unix_data.mode;
                }
        }
        stbuf->st_ino = (ino_t)inode->i_ino;
        stbuf->st_nlink = inode->i_nlink;
        if (lte)
                stbuf->st_size = lte->size;
        else
                stbuf->st_size = 0;
#ifdef HAVE_STAT_NANOSECOND_PRECISION
        stbuf->st_atim = wim_timestamp_to_timespec(inode->i_last_access_time);
        stbuf->st_mtim = wim_timestamp_to_timespec(inode->i_last_write_time);
        stbuf->st_ctim = stbuf->st_mtim;
#else
        stbuf->st_atime = wim_timestamp_to_unix(inode->i_last_access_time);
        stbuf->st_mtime = wim_timestamp_to_unix(inode->i_last_write_time);
        stbuf->st_ctime = stbuf->st_mtime;
#endif
        stbuf->st_blocks = (stbuf->st_size + 511) / 512;
        return 0;
}

static void
touch_inode(struct wim_inode *inode)
{
        u64 now = get_wim_timestamp();
        inode->i_last_access_time = now;
        inode->i_last_write_time = now;
}

/* Creates a new staging file and returns its file descriptor opened for
 * writing.
 *
 * @name_ret: A location into which the a pointer to the newly allocated name of
 *            the staging file is stored.
 *
 * @ctx:      Context for the WIM filesystem; this provides the name of the
 *            staging directory.
 *
 * On success, returns the file descriptor for the staging file, opened for
 * writing.  On failure, returns -1 and sets errno.
 */
static int
create_staging_file(char **name_ret, struct wimfs_context *ctx)
{
        size_t name_len;
        char *name;
        struct stat stbuf;
        int fd;
        int errno_save;

        static const size_t STAGING_FILE_NAME_LEN = 20;

        name_len = ctx->staging_dir_name_len + 1 + STAGING_FILE_NAME_LEN;
        name = MALLOC(name_len + 1);
        if (!name) {
                errno = ENOMEM;
                return -1;
        }

        do {

                memcpy(name, ctx->staging_dir_name, ctx->staging_dir_name_len);
                name[ctx->staging_dir_name_len] = '/';
                randomize_char_array_with_alnum(name + ctx->staging_dir_name_len + 1,
                                                STAGING_FILE_NAME_LEN);
                name[name_len] = '\0';


        /* Just in case, verify that the randomly generated name doesn't name an
         * existing file, and try again if so  */
        } while (stat(name, &stbuf) == 0);

        if (errno != ENOENT) /* other error?! */
                return -1;

        /* doesn't exist--- ok */

        DEBUG("Creating staging file `%s'", name);

        fd = open(name, O_WRONLY | O_CREAT | O_EXCL, 0600);
        if (fd == -1) {
                errno_save = errno;
                FREE(name);
                errno = errno_save;
        } else {
                *name_ret = name;
        }
        return fd;
}

/*
 * Extract a WIM resource to the staging directory.
 *
 * @inode:  Inode that contains the stream we are extracting
 *
 * @stream_id: Identifier for the stream (it stays constant even if the indices
 * of the stream entries are changed)
 *
 * @lte: Pointer to pointer to the lookup table entry for the stream we need to
 * extract, or NULL if there was no lookup table entry present for the stream
 *
 * @size:  Number of bytes of the stream we want to extract (this supports the
 * wimfs_truncate() function).  It may be more than the actual stream length, in
 * which case the extra space is filled with zeroes.
 *
 * @ctx:  Context for the WIM filesystem.
 *
 * Returns 0 on success or a negative error code on failure.
 */
static int
extract_resource_to_staging_dir(struct wim_inode *inode,
                                u32 stream_id,
                                struct wim_lookup_table_entry **lte,
                                off_t size,
                                struct wimfs_context *ctx)
{
        char *staging_file_name;
        int ret;
        int fd;
        struct wim_lookup_table_entry *old_lte, *new_lte;
        off_t extract_size;

        DEBUG("Extracting resource to staging dir: inode %"PRIu64", "
              "stream id %"PRIu32, inode->i_ino, stream_id);

        old_lte = *lte;

        wimlib_assert(old_lte == NULL ||
                      old_lte->resource_location != RESOURCE_IN_STAGING_FILE);

        /* Create the staging file */
        fd = create_staging_file(&staging_file_name, ctx);
        if (fd == -1)
                return -errno;

        /* Extract the stream to the staging file (possibly truncated) */
        if (old_lte) {
                struct filedes wimlib_fd;
                filedes_init(&wimlib_fd, fd);
                extract_size = min(old_lte->size, size);
                ret = extract_stream_to_fd(old_lte, &wimlib_fd, extract_size);
        } else {
                ret = 0;
                extract_size = 0;
        }

        /* In the case of truncate() to more than the file length, extend the
         * file with zeroes by calling ftruncate() on the underlying staging
         * file */
        if (ret == 0 && size > extract_size)
                ret = ftruncate(fd, size);

        /* Close the staging file descriptor and check for errors.  If there's
         * an error, unlink the staging file. */
        if (ret != 0 || close(fd) != 0) {
                if (errno != 0)
                        ret = -errno;
                else
                        ret = -EIO;
                close(fd);
                goto out_delete_staging_file;
        }

        /* Now deal with the lookup table entries.  We may be able to re-use the
         * existing entry, but we may have to create a new one instead. */

        if (old_lte && inode->i_nlink == old_lte->refcnt) {
                /* The reference count of the existing lookup table entry is the
                 * same as the link count of the inode that contains the stream
                 * we're opening.  Therefore, ALL the references to the lookup
                 * table entry correspond to the stream we're trying to extract,
                 * so the lookup table entry can be re-used.  */
                DEBUG("Re-using lookup table entry");
                lookup_table_unlink(ctx->wim->lookup_table, old_lte);
                new_lte = old_lte;
        } else {
                if (old_lte) {
                        /* There's an existing lookup table entry, but its
                         * reference count is greater than the link count for
                         * the inode containing a stream we're opening.
                         * Therefore, we need to split the lookup table entry.
                         */
                        wimlib_assert(old_lte->refcnt > inode->i_nlink);
                        DEBUG("Splitting lookup table entry "
                              "(inode->i_nlink = %u, old_lte->refcnt = %u)",
                              inode->i_nlink, old_lte->refcnt);
                }

                new_lte = new_lookup_table_entry();
                if (!new_lte) {
                        ret = -ENOMEM;
                        goto out_delete_staging_file;
                }

                /* There may already be open file descriptors to this stream if
                 * it's previously been opened read-only, but just now we're
                 * opening it read-write.  Identify those file descriptors and
                 * change their lookup table entry pointers to point to the new
                 * lookup table entry, and open staging file descriptors for
                 * them.
                 *
                 * At the same time, we need to count the number of these opened
                 * file descriptors to the new lookup table entry.  If there's
                 * an old lookup table entry, this number needs to be subtracted
                 * from the fd's opened to the old entry. */
                for (u16 i = 0, j = 0; j < inode->i_num_opened_fds; i++) {
                        struct wimfs_fd *fd = inode->i_fds[i];
                        if (fd) {
                                if (fd->stream_id == stream_id) {
                                        int raw_fd;

                                        wimlib_assert(fd->f_lte == old_lte);
                                        wimlib_assert(!filedes_valid(&fd->staging_fd));
                                        fd->f_lte = new_lte;
                                        new_lte->num_opened_fds++;
                                        raw_fd = open(staging_file_name, O_RDONLY);
                                        if (raw_fd < 0) {
                                                ret = -errno;
                                                goto out_revert_fd_changes;
                                        }
                                        filedes_init(&fd->staging_fd, raw_fd);
                                }
                                j++;
                        }
                }
                DEBUG("%hu fd's were already opened to the file we extracted",
                      new_lte->num_opened_fds);
                if (old_lte) {
                        old_lte->num_opened_fds -= new_lte->num_opened_fds;
                        old_lte->refcnt -= inode->i_nlink;
                }
        }

        lte_put_resource(new_lte);
        new_lte->refcnt              = inode->i_nlink;
        new_lte->resource_location   = RESOURCE_IN_STAGING_FILE;
        new_lte->staging_file_name   = staging_file_name;
        new_lte->size                = size;

        add_unhashed_stream(new_lte, inode, stream_id,
                            &wim_get_current_image_metadata(ctx->wim)->unhashed_streams);
        *retrieve_lte_pointer(new_lte) = new_lte;
        *lte = new_lte;
        return 0;
out_revert_fd_changes:
        for (u16 i = 0, j = 0; j < new_lte->num_opened_fds; i++) {
                struct wimfs_fd *fd = inode->i_fds[i];
                if (fd && fd->stream_id == stream_id && fd->f_lte == new_lte) {
                        fd->f_lte = old_lte;
                        if (filedes_valid(&fd->staging_fd)) {
                                filedes_close(&fd->staging_fd);
                                filedes_invalidate(&fd->staging_fd);
                        }
                        j++;
                }
        }
        free_lookup_table_entry(new_lte);
out_delete_staging_file:
        unlink(staging_file_name);
        FREE(staging_file_name);
        return ret;
}

/*
 * Creates a randomly named staging directory and saves its name in the
 * filesystem context structure.
 */
static int
make_staging_dir(struct wimfs_context *ctx, const char *user_prefix)
{
        static const size_t random_suffix_len = 10;
        static const char *common_suffix = ".staging";
        static const size_t common_suffix_len = 8;

        char *staging_dir_name = NULL;
        size_t staging_dir_name_len;
        size_t prefix_len;
        const char *wim_basename;
        char *real_user_prefix = NULL;
        int ret;

        if (user_prefix) {
                real_user_prefix = realpath(user_prefix, NULL);
                if (!real_user_prefix) {
                        ERROR_WITH_ERRNO("Could not resolve `%s'",
                                         real_user_prefix);
                        ret = WIMLIB_ERR_NOTDIR;
                        goto out;
                }
                wim_basename = path_basename(ctx->wim->filename);
                prefix_len = strlen(real_user_prefix) + 1 + strlen(wim_basename);
        } else {
                prefix_len = strlen(ctx->wim->filename);
        }

        staging_dir_name_len = prefix_len + common_suffix_len + random_suffix_len;

        staging_dir_name = MALLOC(staging_dir_name_len + 1);
        if (!staging_dir_name) {
                ret = WIMLIB_ERR_NOMEM;
                goto out;
        }

        if (real_user_prefix)
                sprintf(staging_dir_name, "%s/%s", real_user_prefix, wim_basename);
        else
                strcpy(staging_dir_name, ctx->wim->filename);

        strcat(staging_dir_name, common_suffix);

        randomize_char_array_with_alnum(staging_dir_name + prefix_len + common_suffix_len,
                                        random_suffix_len);

        staging_dir_name[staging_dir_name_len] = '\0';

        if (mkdir(staging_dir_name, 0700) != 0) {
                ERROR_WITH_ERRNO("Failed to create temporary directory `%s'",
                                 staging_dir_name);
                ret = WIMLIB_ERR_MKDIR;
        } else {
                ret = 0;
        }
out:
        FREE(real_user_prefix);
        if (ret == 0) {
                ctx->staging_dir_name = staging_dir_name;
                ctx->staging_dir_name_len = staging_dir_name_len;
        } else {
                FREE(staging_dir_name);
        }
        return ret;
}

static int
remove_file_or_directory(const char *fpath, const struct stat *sb,
                         int typeflag, struct FTW *ftwbuf)
{
        if (remove(fpath) == 0)
                return 0;
        else {
                ERROR_WITH_ERRNO("Cannot remove `%s'", fpath);
                return WIMLIB_ERR_DELETE_STAGING_DIR;
        }
}

/*
 * Deletes the staging directory and all the files contained in it.
 */
static int
delete_staging_dir(struct wimfs_context *ctx)
{
        int ret;
        ret = nftw(ctx->staging_dir_name, remove_file_or_directory,
                   10, FTW_DEPTH);
        FREE(ctx->staging_dir_name);
        ctx->staging_dir_name = NULL;
        return ret;
}

static int
inode_close_fds(struct wim_inode *inode)
{
        u16 num_opened_fds = inode->i_num_opened_fds;
        for (u16 i = 0, j = 0; j < num_opened_fds; i++) {
                struct wimfs_fd *fd = inode->i_fds[i];
                if (fd) {
                        wimlib_assert(fd->f_inode == inode);
                        int ret = close_wimfs_fd(fd);
                        if (ret != 0)
                                return ret;
                        j++;
                }
        }
        return 0;
}

/* Overwrites the WIM file, with changes saved. */
static int
rebuild_wim(struct wimfs_context *ctx, int write_flags,
            wimlib_progress_func_t progress_func)
{
        int ret;
        struct wim_lookup_table_entry *lte, *tmp;
        WIMStruct *wim = ctx->wim;
        struct wim_image_metadata *imd = wim_get_current_image_metadata(ctx->wim);

        DEBUG("Closing all staging file descriptors.");
        image_for_each_unhashed_stream_safe(lte, tmp, imd) {
                ret = inode_close_fds(lte->back_inode);
                if (ret)
                        return ret;
        }

        DEBUG("Freeing entries for zero-length streams");
        image_for_each_unhashed_stream_safe(lte, tmp, imd) {
                wimlib_assert(lte->unhashed);
                if (lte->size == 0) {
                        struct wim_lookup_table_entry **back_ptr;
                        back_ptr = retrieve_lte_pointer(lte);
                        *back_ptr = NULL;
                        list_del(&lte->unhashed_list);
                        free_lookup_table_entry(lte);
                }
        }

        xml_update_image_info(wim, wim->current_image);
        ret = wimlib_overwrite(wim, write_flags, 0, progress_func);
        if (ret)
                ERROR("Failed to commit changes to mounted WIM image");
        return ret;
}

/* Simple function that returns the concatenation of 2 strings. */
static char *
strcat_dup(const char *s1, const char *s2, size_t max_len)
{
        size_t len = strlen(s1) + strlen(s2);
        if (len > max_len)
                len = max_len;
        char *p = MALLOC(len + 1);
        if (!p)
                return NULL;
        snprintf(p, len + 1, "%s%s", s1, s2);
        return p;
}

static int
set_message_queue_names(struct wimfs_context *ctx, const char *mount_dir)
{
        static const char *u2d_prefix = "/wimlib-unmount-to-daemon-mq";
        static const char *d2u_prefix = "/wimlib-daemon-to-unmount-mq";
        char *dir_path;
        char *p;
        int ret;

        dir_path = realpath(mount_dir, NULL);
        if (!dir_path) {
                ERROR_WITH_ERRNO("Failed to resolve path \"%s\"", mount_dir);
                if (errno == ENOMEM)
                        return WIMLIB_ERR_NOMEM;
                else
                        return WIMLIB_ERR_NOTDIR;
        }

        for (p = dir_path; *p; p++)
                if (*p == '/')
                        *p = 0xff;

        ctx->unmount_to_daemon_mq_name = strcat_dup(u2d_prefix, dir_path,
                                                    NAME_MAX);
        if (!ctx->unmount_to_daemon_mq_name) {
                ret = WIMLIB_ERR_NOMEM;
                goto out_free_dir_path;
        }
        ctx->daemon_to_unmount_mq_name = strcat_dup(d2u_prefix, dir_path,
                                                    NAME_MAX);
        if (!ctx->daemon_to_unmount_mq_name) {
                ret = WIMLIB_ERR_NOMEM;
                goto out_free_unmount_to_daemon_mq_name;
        }

        ret = 0;
        goto out_free_dir_path;
out_free_unmount_to_daemon_mq_name:
        FREE(ctx->unmount_to_daemon_mq_name);
        ctx->unmount_to_daemon_mq_name = NULL;
out_free_dir_path:
        FREE(dir_path);
        return ret;
}

static void
free_message_queue_names(struct wimfs_context *ctx)
{
        FREE(ctx->unmount_to_daemon_mq_name);
        FREE(ctx->daemon_to_unmount_mq_name);
        ctx->unmount_to_daemon_mq_name = NULL;
        ctx->daemon_to_unmount_mq_name = NULL;
}

/*
 * Opens two POSIX message queue: one for sending messages from the unmount
 * process to the daemon process, and one to go the other way.  The names of the
 * message queues, which must be system-wide unique, are be based on the mount
 * point.
 *
 * @daemon specifies whether the calling process is the filesystem daemon or the
 * unmount process.
 */
static int
open_message_queues(struct wimfs_context *ctx, bool daemon)
{
        int unmount_to_daemon_mq_flags = O_WRONLY | O_CREAT;
        int daemon_to_unmount_mq_flags = O_RDONLY | O_CREAT;
        mode_t mode;
        mode_t orig_umask;
        int ret;

        if (daemon) {
                swap(unmount_to_daemon_mq_flags, daemon_to_unmount_mq_flags);
                mode = 0600;
        } else {
                mode = 0666;
        }

        orig_umask = umask(0000);
        DEBUG("Opening message queue \"%s\"", ctx->unmount_to_daemon_mq_name);
        ctx->unmount_to_daemon_mq = mq_open(ctx->unmount_to_daemon_mq_name,
                                            unmount_to_daemon_mq_flags, mode, NULL);

        if (ctx->unmount_to_daemon_mq == (mqd_t)-1) {
                ERROR_WITH_ERRNO("mq_open()");
                ret = WIMLIB_ERR_MQUEUE;
                goto out;
        }

        DEBUG("Opening message queue \"%s\"", ctx->daemon_to_unmount_mq_name);
        ctx->daemon_to_unmount_mq = mq_open(ctx->daemon_to_unmount_mq_name,
                                            daemon_to_unmount_mq_flags, mode, NULL);

        if (ctx->daemon_to_unmount_mq == (mqd_t)-1) {
                ERROR_WITH_ERRNO("mq_open()");
                mq_close(ctx->unmount_to_daemon_mq);
                mq_unlink(ctx->unmount_to_daemon_mq_name);
                ctx->unmount_to_daemon_mq = (mqd_t)-1;
                ret = WIMLIB_ERR_MQUEUE;
                goto out;
        }
        ret = 0;
out:
        umask(orig_umask);
        return ret;
}

/* Try to determine the maximum message size of a message queue.  The return
 * value is the maximum message size, or a guess of 8192 bytes if it cannot be
 * determined. */
static long
mq_get_msgsize(mqd_t mq)
{
        static const char *msgsize_max_file = "/proc/sys/fs/mqueue/msgsize_max";
        FILE *fp;
        struct mq_attr attr;
        long msgsize;

        if (mq_getattr(mq, &attr) == 0) {
                msgsize = attr.mq_msgsize;
        } else {
                ERROR_WITH_ERRNO("mq_getattr()");
                ERROR("Attempting to read %s", msgsize_max_file);
                fp = fopen(msgsize_max_file, "rb");
                if (fp) {
                        if (fscanf(fp, "%ld", &msgsize) != 1) {
                                ERROR("Assuming message size of 8192");
                                msgsize = 8192;
                        }
                        fclose(fp);
                } else {
                        ERROR_WITH_ERRNO("Failed to open the file `%s'",
                                         msgsize_max_file);
                        ERROR("Assuming message size of 8192");
                        msgsize = 8192;
                }
        }
        return msgsize;
}

static int
get_mailbox(mqd_t mq, long needed_msgsize, long *msgsize_ret,
            void **mailbox_ret)
{
        long msgsize;
        void *mailbox;

        msgsize = mq_get_msgsize(mq);

        if (msgsize < needed_msgsize) {
                ERROR("Message queue max size must be at least %ld!",
                      needed_msgsize);
                return WIMLIB_ERR_MQUEUE;
        }

        mailbox = MALLOC(msgsize);
        if (!mailbox) {
                ERROR("Failed to allocate %ld bytes for mailbox", msgsize);
                return WIMLIB_ERR_NOMEM;
        }
        *msgsize_ret = msgsize;
        *mailbox_ret = mailbox;
        return 0;
}

static void
unlink_message_queues(struct wimfs_context *ctx)
{
        mq_unlink(ctx->unmount_to_daemon_mq_name);
        mq_unlink(ctx->daemon_to_unmount_mq_name);
}

/* Closes the message queues, which are allocated in static variables */
static void
close_message_queues(struct wimfs_context *ctx)
{
        DEBUG("Closing message queues");
        mq_close(ctx->unmount_to_daemon_mq);
        ctx->unmount_to_daemon_mq = (mqd_t)(-1);
        mq_close(ctx->daemon_to_unmount_mq);
        ctx->daemon_to_unmount_mq = (mqd_t)(-1);
        unlink_message_queues(ctx);
}


struct unmount_msg_hdr {
        u32 min_version;
        u32 cur_version;
        u32 msg_type;
        u32 msg_size;
} _packed_attribute;

struct msg_unmount_request {
        struct unmount_msg_hdr hdr;
        u32 unmount_flags;
        u8 want_progress_messages;
} _packed_attribute;

struct msg_daemon_info {
        struct unmount_msg_hdr hdr;
        pid_t daemon_pid;
        u32 mount_flags;
} _packed_attribute;

struct msg_unmount_finished {
        struct unmount_msg_hdr hdr;
        s32 status;
} _packed_attribute;

struct msg_write_streams_progress {
        struct unmount_msg_hdr hdr;
        union wimlib_progress_info info;
} _packed_attribute;

enum {
        MSG_TYPE_UNMOUNT_REQUEST,
        MSG_TYPE_DAEMON_INFO,
        MSG_TYPE_WRITE_STREAMS_PROGRESS,
        MSG_TYPE_UNMOUNT_FINISHED,
        MSG_TYPE_MAX,
};

struct msg_handler_context_hdr {
        int timeout_seconds;
};

struct unmount_msg_handler_context {
        struct msg_handler_context_hdr hdr;
        pid_t daemon_pid;
        int mount_flags;
        int status;
        wimlib_progress_func_t progress_func;
};

struct daemon_msg_handler_context {
        struct msg_handler_context_hdr hdr;
        struct wimfs_context *wimfs_ctx;
};

static int
send_unmount_request_msg(mqd_t mq, int unmount_flags, u8 want_progress_messages)
{
        DEBUG("Sending unmount request msg");
        struct msg_unmount_request msg = {
                .hdr = {
                        .min_version = ((unmount_flags & WIMLIB_UNMOUNT_FLAG_NEW_IMAGE) ?
                                                WIMLIB_MAKEVERSION(1, 6, 2) :
                                                WIMLIB_MAKEVERSION(1, 2, 1)),
                        .cur_version = WIMLIB_VERSION_CODE,
                        .msg_type    = MSG_TYPE_UNMOUNT_REQUEST,
                        .msg_size    = sizeof(msg),
                },
                .unmount_flags = unmount_flags,
                .want_progress_messages = want_progress_messages,
        };

        if (mq_send(mq, (void*)&msg, sizeof(msg), 1)) {
                ERROR_WITH_ERRNO("Failed to communicate with filesystem daemon");
                return WIMLIB_ERR_MQUEUE;
        }
        return 0;
}

static int
send_daemon_info_msg(mqd_t mq, pid_t pid, int mount_flags)
{
        DEBUG("Sending daemon info msg (pid = %d, mount_flags=%x)",
              pid, mount_flags);

        struct msg_daemon_info msg = {
                .hdr = {
                        .min_version = WIMLIB_MAKEVERSION(1, 2, 1),
                        .cur_version = WIMLIB_VERSION_CODE,
                        .msg_type = MSG_TYPE_DAEMON_INFO,
                        .msg_size = sizeof(msg),
                },
                .daemon_pid = pid,
                .mount_flags = mount_flags,
        };
        if (mq_send(mq, (void*)&msg, sizeof(msg), 1)) {
                ERROR_WITH_ERRNO("Failed to send daemon info to unmount process");
                return WIMLIB_ERR_MQUEUE;
        }
        return 0;
}

static void
send_unmount_finished_msg(mqd_t mq, int status)
{
        DEBUG("Sending unmount finished msg");
        struct msg_unmount_finished msg = {
                .hdr = {
                        .min_version = WIMLIB_MAKEVERSION(1, 2, 1),
                        .cur_version = WIMLIB_VERSION_CODE,
                        .msg_type = MSG_TYPE_UNMOUNT_FINISHED,
                        .msg_size = sizeof(msg),
                },
                .status = status,
        };
        if (mq_send(mq, (void*)&msg, sizeof(msg), 1))
                ERROR_WITH_ERRNO("Failed to send status to unmount process");
}

static int
unmount_progress_func(enum wimlib_progress_msg msg,
                      const union wimlib_progress_info *info)
{
        if (msg == WIMLIB_PROGRESS_MSG_WRITE_STREAMS) {
                struct msg_write_streams_progress msg = {
                        .hdr = {
                                .min_version = WIMLIB_MAKEVERSION(1, 2, 1),
                                .cur_version = WIMLIB_VERSION_CODE,
                                .msg_type = MSG_TYPE_WRITE_STREAMS_PROGRESS,
                                .msg_size = sizeof(msg),
                        },
                        .info = *info,
                };
                if (mq_send(wimfs_get_context()->daemon_to_unmount_mq,
                            (void*)&msg, sizeof(msg), 1))
                {
                        ERROR_WITH_ERRNO("Failed to send progress information "
                                         "to unmount process");
                }
        }
        return 0;
}

static void
release_extra_refcnts(struct wimfs_context *ctx)
{
        struct list_head *list = &ctx->orig_stream_list;
        struct wim_lookup_table *lookup_table = ctx->wim->lookup_table;
        struct wim_lookup_table_entry *lte, *tmp;

        list_for_each_entry_safe(lte, tmp, list, orig_stream_list)
                while (lte->out_refcnt--)
                        lte_decrement_refcnt(lte, lookup_table);
}

/* Moves the currently selected image, which may have been modified, to a new
 * index, and sets the original index to refer to a reset (unmodified) copy of
 * the image.  */
static int
renew_current_image(struct wimfs_context *ctx)
{
        WIMStruct *wim = ctx->wim;
        int ret;
        int idx = wim->current_image - 1;
        struct wim_image_metadata *imd = wim->image_metadata[idx];
        struct wim_image_metadata *replace_imd;
        struct wim_lookup_table_entry *new_lte;

        if (imd->metadata_lte->resource_location != RESOURCE_IN_WIM) {
                ERROR("Can't reset modified image that doesn't yet "
                      "exist in the on-disk WIM file!");
                return WIMLIB_ERR_METADATA_NOT_FOUND;
        }

        /* Create 'replace_imd' structure to use for the reset original,
         * unmodified image.  */
        replace_imd = new_image_metadata();
        if (!replace_imd)
                return WIMLIB_ERR_NOMEM;

        /* Create new stream reference for the modified image's metadata
         * resource, which doesn't exist yet.  */
        ret = WIMLIB_ERR_NOMEM;
        new_lte = new_lookup_table_entry();
        if (!new_lte)
                goto err_put_replace_imd;
        new_lte->flags = WIM_RESHDR_FLAG_METADATA;
        new_lte->unhashed = 1;

        /* Make the image being moved available at a new index.  Increments the
         * WIM's image count, but does not increment the reference count of the
         * 'struct image_metadata'.  */
        ret = append_image_metadata(wim, imd);
        if (ret)
                goto err_free_new_lte;

        ret = xml_add_image(wim, T(""));
        if (ret)
                goto err_undo_append;

        replace_imd->metadata_lte = imd->metadata_lte;
        imd->metadata_lte = new_lte;
        wim->image_metadata[idx] = replace_imd;
        wim->current_image = wim->hdr.image_count;
        return 0;

err_undo_append:
        wim->hdr.image_count--;
err_free_new_lte:
        free_lookup_table_entry(new_lte);
err_put_replace_imd:
        put_image_metadata(replace_imd, NULL);
        return ret;
}

static int
msg_unmount_request_handler(const void *_msg, void *_handler_ctx)
{
        const struct msg_unmount_request *msg = _msg;
        struct daemon_msg_handler_context *handler_ctx = _handler_ctx;
        struct wimfs_context *wimfs_ctx;
        int status = 0;
        int ret;
        int unmount_flags;
        wimlib_progress_func_t progress_func;

        DEBUG("Handling unmount request msg");

        wimfs_ctx = handler_ctx->wimfs_ctx;
        if (msg->hdr.msg_size < sizeof(*msg)) {
                status = WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
                goto out;
        }

        unmount_flags = msg->unmount_flags;
        if (msg->want_progress_messages)
                progress_func = unmount_progress_func;
        else
                progress_func = NULL;

        ret = send_daemon_info_msg(wimfs_ctx->daemon_to_unmount_mq, getpid(),
                                   wimfs_ctx->mount_flags);
        if (ret != 0) {
                status = ret;
                goto out;
        }

        if (wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                if (unmount_flags & WIMLIB_UNMOUNT_FLAG_COMMIT) {

                        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_NEW_IMAGE) {
                                ret = renew_current_image(wimfs_ctx);
                                if (ret) {
                                        status = ret;
                                        goto out;
                                }
                        } else {
                                release_extra_refcnts(wimfs_ctx);
                        }
                        INIT_LIST_HEAD(&wimfs_ctx->orig_stream_list);

                        int write_flags = 0;
                        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_CHECK_INTEGRITY)
                                write_flags |= WIMLIB_WRITE_FLAG_CHECK_INTEGRITY;
                        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_REBUILD)
                                write_flags |= WIMLIB_WRITE_FLAG_REBUILD;
                        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_RECOMPRESS)
                                write_flags |= WIMLIB_WRITE_FLAG_RECOMPRESS;
                        status = rebuild_wim(wimfs_ctx, write_flags,
                                             progress_func);
                }
        } else {
                DEBUG("Read-only mount");
                status = 0;
        }

out:
        if (wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                ret = delete_staging_dir(wimfs_ctx);
                if (ret != 0) {
                        ERROR("Failed to delete the staging directory");
                        if (status == 0)
                                status = ret;
                }
        }
        wimfs_ctx->status = status;
        wimfs_ctx->have_status = true;
        return MSG_BREAK_LOOP;
}

static int
msg_daemon_info_handler(const void *_msg, void *_handler_ctx)
{
        const struct msg_daemon_info *msg = _msg;
        struct unmount_msg_handler_context *handler_ctx = _handler_ctx;

        DEBUG("Handling daemon info msg");
        if (msg->hdr.msg_size < sizeof(*msg))
                return WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        handler_ctx->daemon_pid = msg->daemon_pid;
        handler_ctx->mount_flags = msg->mount_flags;
        handler_ctx->hdr.timeout_seconds = 1;
        DEBUG("pid of daemon is %d; mount flags were %#x",
              handler_ctx->daemon_pid,
              handler_ctx->mount_flags);
        return 0;
}

static int
msg_write_streams_progress_handler(const void *_msg, void *_handler_ctx)
{
        const struct msg_write_streams_progress *msg = _msg;
        struct unmount_msg_handler_context *handler_ctx = _handler_ctx;

        if (msg->hdr.msg_size < sizeof(*msg))
                return WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        if (handler_ctx->progress_func) {
                handler_ctx->progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
                                           &msg->info);
        }
        return 0;
}

static int
msg_unmount_finished_handler(const void *_msg, void *_handler_ctx)
{
        const struct msg_unmount_finished *msg = _msg;
        struct unmount_msg_handler_context *handler_ctx = _handler_ctx;

        DEBUG("Handling unmount finished message");
        if (msg->hdr.msg_size < sizeof(*msg))
                return WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        handler_ctx->status = msg->status;
        DEBUG("status is %d", handler_ctx->status);
        return MSG_BREAK_LOOP;
}

static int
unmount_timed_out_cb(void *_handler_ctx)
{
        const struct unmount_msg_handler_context *handler_ctx = _handler_ctx;

        if (handler_ctx->daemon_pid == 0 ||
            (kill(handler_ctx->daemon_pid, 0) != 0 && errno == ESRCH))
        {
                ERROR("The filesystem daemon has crashed!  Changes to the "
                      "WIM may not have been commited.");
                return WIMLIB_ERR_FILESYSTEM_DAEMON_CRASHED;
        }

        DEBUG("Filesystem daemon is still alive... "
              "Waiting another %d seconds", handler_ctx->hdr.timeout_seconds);
        return 0;
}

static int
daemon_timed_out_cb(void *_handler_ctx)
{
        ERROR("Timed out waiting for unmount request! "
              "Changes to the mounted WIM will not be committed.");
        return WIMLIB_ERR_TIMEOUT;
}

typedef int (*msg_handler_t)(const void *_msg, void *_handler_ctx);

struct msg_handler_callbacks {
        int (*timed_out)(void * _handler_ctx);
        msg_handler_t msg_handlers[MSG_TYPE_MAX];
};

static const struct msg_handler_callbacks unmount_msg_handler_callbacks = {
        .timed_out = unmount_timed_out_cb,
        .msg_handlers = {
                [MSG_TYPE_DAEMON_INFO] = msg_daemon_info_handler,
                [MSG_TYPE_WRITE_STREAMS_PROGRESS] = msg_write_streams_progress_handler,
                [MSG_TYPE_UNMOUNT_FINISHED] = msg_unmount_finished_handler,
        },
};

static const struct msg_handler_callbacks daemon_msg_handler_callbacks = {
        .timed_out = daemon_timed_out_cb,
        .msg_handlers = {
                [MSG_TYPE_UNMOUNT_REQUEST] = msg_unmount_request_handler,
        },
};

static int
receive_message(mqd_t mq,
                struct msg_handler_context_hdr *handler_ctx,
                const msg_handler_t msg_handlers[],
                long mailbox_size, void *mailbox)
{
        struct timeval now;
        struct timespec timeout;
        ssize_t bytes_received;
        struct unmount_msg_hdr *hdr;
        int ret;

        gettimeofday(&now, NULL);
        timeout.tv_sec = now.tv_sec + handler_ctx->timeout_seconds;
        timeout.tv_nsec = now.tv_usec * 1000;

        bytes_received = mq_timedreceive(mq, mailbox,
                                         mailbox_size, NULL, &timeout);
        hdr = mailbox;
        if (bytes_received == -1) {
                if (errno == ETIMEDOUT) {
                        ret = WIMLIB_ERR_TIMEOUT;
                } else {
                        ERROR_WITH_ERRNO("mq_timedreceive()");
                        ret = WIMLIB_ERR_MQUEUE;
                }
        } else if (bytes_received < sizeof(*hdr) ||
                   bytes_received != hdr->msg_size) {
                ret = WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        } else if (WIMLIB_VERSION_CODE < hdr->min_version) {
                /*ERROR("Cannot understand the received message. "*/
                      /*"Please upgrade wimlib to at least v%d.%d.%d",*/
                      /*WIMLIB_GET_MAJOR_VERSION(hdr->min_version),*/
                      /*WIMLIB_GET_MINOR_VERSION(hdr->min_version),*/
                      /*WIMLIB_GET_PATCH_VERSION(hdr->min_version));*/
                ret = MSG_VERSION_TOO_HIGH;
        } else if (hdr->msg_type >= MSG_TYPE_MAX) {
                ret = WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        } else if (msg_handlers[hdr->msg_type] == NULL) {
                ret = WIMLIB_ERR_INVALID_UNMOUNT_MESSAGE;
        } else {
                ret = msg_handlers[hdr->msg_type](mailbox, handler_ctx);
        }
        return ret;
}

static int
message_loop(mqd_t mq,
             const struct msg_handler_callbacks *callbacks,
             struct msg_handler_context_hdr *handler_ctx)
{
        static const size_t MAX_MSG_SIZE = 512;
        long msgsize;
        void *mailbox;
        int ret;

        DEBUG("Entering message loop");

        ret = get_mailbox(mq, MAX_MSG_SIZE, &msgsize, &mailbox);
        if (ret != 0)
                return ret;
        while (1) {
                ret = receive_message(mq, handler_ctx,
                                      callbacks->msg_handlers,
                                      msgsize, mailbox);
                if (ret == 0 || ret == MSG_VERSION_TOO_HIGH) {
                        continue;
                } else if (ret == MSG_BREAK_LOOP) {
                        ret = 0;
                        break;
                } else if (ret == WIMLIB_ERR_TIMEOUT) {
                        if (callbacks->timed_out)
                                ret = callbacks->timed_out(handler_ctx);
                        if (ret == 0)
                                continue;
                        else
                                break;
                } else {
                        ERROR_WITH_ERRNO("Error communicating with "
                                         "filesystem daemon");
                        break;
                }
        }
        FREE(mailbox);
        DEBUG("Exiting message loop");
        return ret;
}

/* Execute `fusermount -u', which is installed setuid root, to unmount the WIM.
 *
 * FUSE does not yet implement synchronous unmounts.  This means that fusermount
 * -u will return before the filesystem daemon returns from wimfs_destroy().
 *  This is partly what we want, because we need to send a message from this
 *  process to the filesystem daemon telling whether --commit was specified or
 *  not.  However, after that, the unmount process must wait for the filesystem
 *  daemon to finish writing the WIM file.
 */
static int
execute_fusermount(const char *dir, bool lazy)
{
        pid_t pid;
        int ret;
        int status;

        pid = fork();
        if (pid == -1) {
                ERROR_WITH_ERRNO("Failed to fork()");
                return WIMLIB_ERR_FORK;
        }
        if (pid == 0) {
                /* Child */
                char *argv[10];
                char **argp = argv;
                *argp++ = "fusermount";
                if (lazy)
                        *argp++ = "-z";
                *argp++ = "-u";
                *argp++ = (char*)dir;
                *argp = NULL;
                execvp("fusermount", argv);
                ERROR_WITH_ERRNO("Failed to execute `fusermount'");
                exit(WIMLIB_ERR_FUSERMOUNT);
        }

        /* Parent */
        ret = waitpid(pid, &status, 0);
        if (ret == -1) {
                ERROR_WITH_ERRNO("Failed to wait for fusermount process to "
                                 "terminate");
                return WIMLIB_ERR_FUSERMOUNT;
        }

        if (!WIFEXITED(status)) {
                ERROR("'fusermount' did not terminate normally!");
                return WIMLIB_ERR_FUSERMOUNT;
        }

        status = WEXITSTATUS(status);

        if (status == 0)
                return 0;

        if (status != WIMLIB_ERR_FUSERMOUNT)
                return WIMLIB_ERR_FUSERMOUNT;

        /* Try again, but with the `umount' program.  This is required on other
         * FUSE implementations such as FreeBSD's that do not have a
         * `fusermount' program. */
        ERROR("Falling back to 'umount'.  Note: you may need to be "
              "root for this to work");
        pid = fork();
        if (pid == -1) {
                ERROR_WITH_ERRNO("Failed to fork()");
                return WIMLIB_ERR_FORK;
        }
        if (pid == 0) {
                /* Child */
                char *argv[10];
                char **argp = argv;
                *argp++ = "umount";
                if (lazy)
                        *argp++ = "-l";
                *argp++ = (char*)dir;
                *argp = NULL;
                execvp("umount", argv);
                ERROR_WITH_ERRNO("Failed to execute `umount'");
                exit(WIMLIB_ERR_FUSERMOUNT);
        }

        /* Parent */
        ret = waitpid(pid, &status, 0);
        if (ret == -1) {
                ERROR_WITH_ERRNO("Failed to wait for `umount' process to "
                                 "terminate");
                return WIMLIB_ERR_FUSERMOUNT;
        }

        if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
                ERROR("`umount' did not successfully complete");
                return WIMLIB_ERR_FUSERMOUNT;
        }

        return 0;
}

static int
wimfs_chmod(const char *path, mode_t mask)
{
        struct wim_dentry *dentry;
        struct wimfs_context *ctx = wimfs_get_context();
        int ret;

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA))
                return -EPERM;

        ret = wim_pathname_to_stream(ctx->wim, path, LOOKUP_FLAG_DIRECTORY_OK,
                                     &dentry, NULL, NULL);
        if (ret)
                return ret;

        ret = inode_set_unix_data(dentry->d_inode, ctx->default_uid,
                                  ctx->default_gid, mask,
                                  ctx->wim->lookup_table, UNIX_DATA_MODE);
        return ret ? -ENOMEM : 0;
}

static int
wimfs_chown(const char *path, uid_t uid, gid_t gid)
{
        struct wim_dentry *dentry;
        struct wimfs_context *ctx = wimfs_get_context();
        int ret;

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA))
                return -EPERM;

        ret = wim_pathname_to_stream(ctx->wim, path, LOOKUP_FLAG_DIRECTORY_OK,
                                     &dentry, NULL, NULL);
        if (ret)
                return ret;

        ret = inode_set_unix_data(dentry->d_inode, uid, gid,
                                  inode_default_unix_mode(dentry->d_inode),
                                  ctx->wim->lookup_table,
                                  UNIX_DATA_UID | UNIX_DATA_GID);
        return ret ? -ENOMEM : 0;
}

/* Called when the filesystem is unmounted. */
static void
wimfs_destroy(void *p)
{
        struct wimfs_context *wimfs_ctx = wimfs_get_context();
        if (open_message_queues(wimfs_ctx, true) == 0) {
                struct daemon_msg_handler_context handler_ctx = {
                        .hdr = {
                                .timeout_seconds = 5,
                        },
                        .wimfs_ctx = wimfs_ctx,
                };
                message_loop(wimfs_ctx->unmount_to_daemon_mq,
                             &daemon_msg_handler_callbacks,
                             &handler_ctx.hdr);
        }
}

static int
wimfs_fgetattr(const char *path, struct stat *stbuf,
               struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        return inode_to_stbuf(fd->f_inode, fd->f_lte, stbuf);
}

static int
wimfs_ftruncate(const char *path, off_t size, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        int ret = ftruncate(fd->staging_fd.fd, size);
        if (ret)
                return -errno;
        touch_inode(fd->f_inode);
        fd->f_lte->size = size;
        return 0;
}

/*
 * Fills in a `struct stat' that corresponds to a file or directory in the WIM.
 */
static int
wimfs_getattr(const char *path, struct stat *stbuf)
{
        struct wim_dentry *dentry;
        struct wim_lookup_table_entry *lte;
        int ret;
        struct wimfs_context *ctx = wimfs_get_context();

        ret = wim_pathname_to_stream(ctx->wim, path,
                                     get_lookup_flags(ctx) |
                                        LOOKUP_FLAG_DIRECTORY_OK,
                                     &dentry, &lte, NULL);
        if (ret != 0)
                return ret;
        return inode_to_stbuf(dentry->d_inode, lte, stbuf);
}

#ifdef ENABLE_XATTR
/* Read an alternate data stream through the XATTR interface, or get its size */
static int
wimfs_getxattr(const char *path, const char *name, char *value,
               size_t size)
{
        int ret;
        struct wim_inode *inode;
        struct wim_ads_entry *ads_entry;
        u64 stream_size;
        struct wim_lookup_table_entry *lte;
        struct wimfs_context *ctx = wimfs_get_context();

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR))
                return -ENOTSUP;

        if (strlen(name) <= 5 || memcmp(name, "user.", 5) != 0)
                return -ENOATTR;
        name += 5;

        inode = wim_pathname_to_inode(ctx->wim, path);
        if (!inode)
                return -errno;

        ads_entry = inode_get_ads_entry(inode, name, NULL);
        if (!ads_entry)
                return -ENOATTR;

        lte = ads_entry->lte;
        stream_size = lte->size;

        if (size == 0)
                return stream_size;

        if (stream_size > size)
                return -ERANGE;

        ret = read_full_stream_into_buf(lte, value);
        if (ret) {
                if (errno)
                        return -errno;
                else
                        return -EIO;
        }
        return stream_size;
}
#endif

/* Create a hard link */
static int
wimfs_link(const char *to, const char *from)
{
        struct wim_dentry *from_dentry, *from_dentry_parent;
        const char *link_name;
        struct wim_inode *inode;
        WIMStruct *wim = wimfs_get_WIMStruct();
        int ret;

        inode = wim_pathname_to_inode(wim, to);
        if (!inode)
                return -errno;

        if (inode->i_attributes & (FILE_ATTRIBUTE_DIRECTORY |
                                   FILE_ATTRIBUTE_REPARSE_POINT))
                return -EPERM;

        from_dentry_parent = get_parent_dentry(wim, from, WIMLIB_CASE_SENSITIVE);
        if (!from_dentry_parent)
                return -errno;
        if (!dentry_is_directory(from_dentry_parent))
                return -ENOTDIR;

        link_name = path_basename(from);
        if (get_dentry_child_with_name(from_dentry_parent, link_name,
                                       WIMLIB_CASE_SENSITIVE))
                return -EEXIST;

        ret = new_dentry(link_name, &from_dentry);
        if (ret)
                return -ENOMEM;

        inode->i_nlink++;
        inode_ref_streams(inode);
        from_dentry->d_inode = inode;
        inode_add_dentry(from_dentry, inode);
        dentry_add_child(from_dentry_parent, from_dentry);
        return 0;
}

#ifdef ENABLE_XATTR
static int
wimfs_listxattr(const char *path, char *list, size_t size)
{
        size_t needed_size;
        struct wim_inode *inode;
        struct wimfs_context *ctx = wimfs_get_context();
        u16 i;
        char *p;
        bool size_only = (size == 0);

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR))
                return -ENOTSUP;

        /* List alternate data streams, or get the list size */

        inode = wim_pathname_to_inode(ctx->wim, path);
        if (!inode)
                return -errno;

        p = list;
        for (i = 0; i < inode->i_num_ads; i++) {

                if (!ads_entry_is_named_stream(&inode->i_ads_entries[i]))
                        continue;

                char *stream_name_mbs;
                size_t stream_name_mbs_nbytes;
                int ret;

                ret = utf16le_to_tstr(inode->i_ads_entries[i].stream_name,
                                      inode->i_ads_entries[i].stream_name_nbytes,
                                      &stream_name_mbs,
                                      &stream_name_mbs_nbytes);
                if (ret)
                        return -errno;

                needed_size = stream_name_mbs_nbytes + 6;
                if (!size_only) {
                        if (needed_size > size) {
                                FREE(stream_name_mbs);
                                return -ERANGE;
                        }
                        sprintf(p, "user.%s", stream_name_mbs);
                        size -= needed_size;
                }
                p += needed_size;
                FREE(stream_name_mbs);
        }
        return p - list;
}
#endif


/* Create a directory in the WIM image. */
static int
wimfs_mkdir(const char *path, mode_t mode)
{
        return create_dentry(fuse_get_context(), path, mode | S_IFDIR,
                             FILE_ATTRIBUTE_DIRECTORY, NULL);
}

/* Create a regular file or alternate data stream in the WIM image. */
static int
wimfs_mknod(const char *path, mode_t mode, dev_t rdev)
{
        const char *stream_name;
        struct fuse_context *fuse_ctx = fuse_get_context();
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);

        if (!S_ISREG(mode))
                return -EPERM;

        if ((wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS)
             && (stream_name = path_stream_name(path))) {
                /* Make an alternate data stream */
                struct wim_ads_entry *new_entry;
                struct wim_inode *inode;

                char *p = (char*)stream_name - 1;
                wimlib_assert(*p == ':');
                *p = '\0';

                inode = wim_pathname_to_inode(wimfs_ctx->wim, path);
                if (!inode)
                        return -errno;
                if (inode->i_attributes & FILE_ATTRIBUTE_REPARSE_POINT)
                        return -ENOENT;
                if (inode_get_ads_entry(inode, stream_name, NULL))
                        return -EEXIST;
                new_entry = inode_add_ads(inode, stream_name);
                if (!new_entry)
                        return -ENOMEM;
                return 0;
        } else {
                /* Make a normal file (not an alternate data stream) */
                return create_dentry(fuse_ctx, path, mode | S_IFREG,
                                     FILE_ATTRIBUTE_NORMAL, NULL);
        }
}

/* Open a file.  */
static int
wimfs_open(const char *path, struct fuse_file_info *fi)
{
        struct wim_dentry *dentry;
        struct wim_lookup_table_entry *lte;
        int ret;
        struct wimfs_fd *fd;
        struct wim_inode *inode;
        u16 stream_idx;
        u32 stream_id;
        struct wimfs_context *ctx = wimfs_get_context();
        struct wim_lookup_table_entry **back_ptr;

        ret = wim_pathname_to_stream(ctx->wim, path, get_lookup_flags(ctx),
                                     &dentry, &lte, &stream_idx);
        if (ret)
                return ret;

        inode = dentry->d_inode;

        if (stream_idx == 0) {
                stream_id = 0;
                back_ptr = &inode->i_lte;
        } else {
                stream_id = inode->i_ads_entries[stream_idx - 1].stream_id;
                back_ptr = &inode->i_ads_entries[stream_idx - 1].lte;
        }

        /* The file resource may be in the staging directory (read-write mounts
         * only) or in the WIM.  If it's in the staging directory, we need to
         * open a native file descriptor for the corresponding file.  Otherwise,
         * we can read the file resource directly from the WIM file if we are
         * opening it read-only, but we need to extract the resource to the
         * staging directory if we are opening it writable. */

        if (flags_writable(fi->flags) &&
            (!lte || lte->resource_location != RESOURCE_IN_STAGING_FILE)) {
                u64 size = (lte) ? lte->size : 0;
                ret = extract_resource_to_staging_dir(inode, stream_id,
                                                      &lte, size, ctx);
                if (ret)
                        return ret;
                *back_ptr = lte;
        }

        ret = alloc_wimfs_fd(inode, stream_id, lte, &fd);
        if (ret)
                return ret;

        if (lte && lte->resource_location == RESOURCE_IN_STAGING_FILE) {
                int raw_fd;

                raw_fd = open(lte->staging_file_name, fi->flags);
                if (raw_fd < 0) {
                        int errno_save = errno;
                        close_wimfs_fd(fd);
                        return -errno_save;
                }
                filedes_init(&fd->staging_fd, raw_fd);
        }
        fi->fh = (uintptr_t)fd;
        return 0;
}

/* Opens a directory. */
static int
wimfs_opendir(const char *path, struct fuse_file_info *fi)
{
        struct wim_inode *inode;
        int ret;
        struct wimfs_fd *fd = NULL;
        struct wimfs_context *ctx = wimfs_get_context();
        WIMStruct *wim = ctx->wim;

        inode = wim_pathname_to_inode(wim, path);
        if (!inode)
                return -errno;
        if (!inode_is_directory(inode))
                return -ENOTDIR;
        ret = alloc_wimfs_fd(inode, 0, NULL, &fd);
        fi->fh = (uintptr_t)fd;
        return ret;
}


/*
 * Read data from a file in the WIM or in the staging directory.
 */
static int
wimfs_read(const char *path, char *buf, size_t size,
           off_t offset, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        ssize_t ret;
        u64 stream_size;

        if (!fd)
                return -EBADF;

        if (size == 0)
                return 0;

        if (fd->f_lte)
                stream_size = fd->f_lte->size;
        else
                stream_size = 0;

        if (offset > stream_size)
                return -EOVERFLOW;

        size = min(size, stream_size - offset);
        if (size == 0)
                return 0;

        switch (fd->f_lte->resource_location) {
        case RESOURCE_IN_STAGING_FILE:
                ret = raw_pread(&fd->staging_fd, buf, size, offset);
                if (ret == -1)
                        ret = -errno;
                break;
        case RESOURCE_IN_WIM:
                if (read_partial_wim_stream_into_buf(fd->f_lte, size,
                                                     offset, buf))
                        ret = errno ? -errno : -EIO;
                else
                        ret = size;
                break;
        case RESOURCE_IN_ATTACHED_BUFFER:
                memcpy(buf, fd->f_lte->attached_buffer + offset, size);
                ret = size;
                break;
        default:
                ERROR("Invalid resource location");
                ret = -EIO;
                break;
        }
        return ret;
}

/* Fills in the entries of the directory specified by @path using the
 * FUSE-provided function @filler.  */
static int
wimfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
              off_t offset, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        struct wim_inode *inode;
        struct wim_dentry *child;
        int ret;

        if (!fd)
                return -EBADF;

        inode = fd->f_inode;

        ret = filler(buf, ".", NULL, 0);
        if (ret)
                return ret;
        ret = filler(buf, "..", NULL, 0);
        if (ret)
                return ret;

        for_inode_child(child, inode) {
                char *file_name_mbs;
                size_t file_name_mbs_nbytes;

                ret = utf16le_to_tstr(child->file_name,
                                      child->file_name_nbytes,
                                      &file_name_mbs,
                                      &file_name_mbs_nbytes);
                if (ret)
                        return -errno;

                ret = filler(buf, file_name_mbs, NULL, 0);
                FREE(file_name_mbs);
                if (ret)
                        return ret;
        }
        return 0;
}


static int
wimfs_readlink(const char *path, char *buf, size_t buf_len)
{
        struct wimfs_context *ctx = wimfs_get_context();
        struct wim_inode *inode = wim_pathname_to_inode(ctx->wim, path);
        int ret;
        if (!inode)
                return -errno;
        if (!inode_is_symlink(inode))
                return -EINVAL;
        if (buf_len == 0)
                return -EINVAL;
        ret = wim_inode_readlink(inode, buf, buf_len - 1, NULL);
        if (ret >= 0) {
                wimlib_assert(ret <= buf_len - 1);
                buf[ret] = '\0';
                ret = 0;
        } else if (ret == -ENAMETOOLONG) {
                buf[buf_len - 1] = '\0';
        }
        return ret;
}

/* Close a file. */
static int
wimfs_release(const char *path, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        return close_wimfs_fd(fd);
}

/* Close a directory */
static int
wimfs_releasedir(const char *path, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        return close_wimfs_fd(fd);
}

#ifdef ENABLE_XATTR
/* Remove an alternate data stream through the XATTR interface */
static int
wimfs_removexattr(const char *path, const char *name)
{
        struct wim_inode *inode;
        struct wim_ads_entry *ads_entry;
        u16 ads_idx;
        struct wimfs_context *ctx = wimfs_get_context();

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR))
                return -ENOTSUP;

        if (strlen(name) < 5 || memcmp(name, "user.", 5) != 0)
                return -ENOATTR;
        name += 5;

        inode = wim_pathname_to_inode(ctx->wim, path);
        if (!inode)
                return -errno;

        ads_entry = inode_get_ads_entry(inode, name, &ads_idx);
        if (!ads_entry)
                return -ENOATTR;
        inode_remove_ads(inode, ads_idx, ctx->wim->lookup_table);
        return 0;
}
#endif

/* Renames a file or directory.  See rename (3) */
static int
wimfs_rename(const char *from, const char *to)
{
        return rename_wim_path(wimfs_get_WIMStruct(), from, to,
                               WIMLIB_CASE_SENSITIVE);
}

/* Remove a directory */
static int
wimfs_rmdir(const char *path)
{
        struct wim_dentry *dentry;
        WIMStruct *wim = wimfs_get_WIMStruct();

        dentry = get_dentry(wim, path, WIMLIB_CASE_SENSITIVE);
        if (!dentry)
                return -errno;

        if (!dentry_is_directory(dentry))
                return -ENOTDIR;

        if (dentry_has_children(dentry))
                return -ENOTEMPTY;

        remove_dentry(dentry, wim->lookup_table);
        return 0;
}

#ifdef ENABLE_XATTR
/* Write an alternate data stream through the XATTR interface */
static int
wimfs_setxattr(const char *path, const char *name,
               const char *value, size_t size, int flags)
{
        struct wim_ads_entry *existing_ads_entry;
        struct wim_inode *inode;
        u16 ads_idx;
        struct wimfs_context *ctx = wimfs_get_context();
        int ret;

        if (!(ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR))
                return -ENOTSUP;

        if (strlen(name) <= 5 || memcmp(name, "user.", 5) != 0)
                return -ENOATTR;
        name += 5;

        inode = wim_pathname_to_inode(ctx->wim, path);
        if (!inode)
                return -errno;

        existing_ads_entry = inode_get_ads_entry(inode, name, &ads_idx);
        if (existing_ads_entry) {
                if (flags & XATTR_CREATE)
                        return -EEXIST;
        } else {
                if (flags & XATTR_REPLACE)
                        return -ENOATTR;
        }

        ret = inode_add_ads_with_data(inode, name, value,
                                      size, ctx->wim->lookup_table);
        if (ret == 0) {
                if (existing_ads_entry)
                        inode_remove_ads(inode, ads_idx, ctx->wim->lookup_table);
        } else {
                ret = -ENOMEM;
        }
        return ret;
}
#endif

static int
wimfs_symlink(const char *to, const char *from)
{
        struct fuse_context *fuse_ctx = fuse_get_context();
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);
        struct wim_dentry *dentry;
        int ret;

        ret = create_dentry(fuse_ctx, from, S_IFLNK | 0777,
                            FILE_ATTRIBUTE_REPARSE_POINT, &dentry);
        if (ret == 0) {
                dentry->d_inode->i_reparse_tag = WIM_IO_REPARSE_TAG_SYMLINK;
                ret = wim_inode_set_symlink(dentry->d_inode, to,
                                            wimfs_ctx->wim->lookup_table);
                if (ret) {
                        remove_dentry(dentry, wimfs_ctx->wim->lookup_table);
                        if (ret == WIMLIB_ERR_NOMEM)
                                ret = -ENOMEM;
                        else
                                ret = -EIO;
                }
        }
        return ret;
}


/* Reduce the size of a file */
static int
wimfs_truncate(const char *path, off_t size)
{
        struct wim_dentry *dentry;
        struct wim_lookup_table_entry *lte;
        int ret;
        u16 stream_idx;
        u32 stream_id;
        struct wim_inode *inode;
        struct wimfs_context *ctx = wimfs_get_context();

        ret = wim_pathname_to_stream(ctx->wim, path, get_lookup_flags(ctx),
                                     &dentry, &lte, &stream_idx);

        if (ret != 0)
                return ret;

        if (lte == NULL && size == 0)
                return 0;

        if (lte != NULL && lte->resource_location == RESOURCE_IN_STAGING_FILE) {
                ret = truncate(lte->staging_file_name, size);
                if (ret)
                        ret = -errno;
                else
                        lte->size = size;
        } else {
                /* File in WIM.  Extract it to the staging directory, but only
                 * the first @size bytes of it. */
                struct wim_lookup_table_entry **back_ptr;

                inode = dentry->d_inode;
                if (stream_idx == 0) {
                        stream_id = 0;
                        back_ptr = &inode->i_lte;
                } else {
                        stream_id = inode->i_ads_entries[stream_idx - 1].stream_id;
                        back_ptr = &inode->i_ads_entries[stream_idx - 1].lte;
                }
                ret = extract_resource_to_staging_dir(inode, stream_id,
                                                      &lte, size, ctx);
                *back_ptr = lte;
        }
        return ret;
}

/* Unlink a non-directory or alternate data stream */
static int
wimfs_unlink(const char *path)
{
        struct wim_dentry *dentry;
        struct wim_lookup_table_entry *lte;
        int ret;
        u16 stream_idx;
        struct wimfs_context *ctx = wimfs_get_context();

        ret = wim_pathname_to_stream(ctx->wim, path, get_lookup_flags(ctx),
                                     &dentry, &lte, &stream_idx);

        if (ret != 0)
                return ret;

        if (inode_stream_name_nbytes(dentry->d_inode, stream_idx) == 0)
                remove_dentry(dentry, ctx->wim->lookup_table);
        else
                inode_remove_ads(dentry->d_inode, stream_idx - 1,
                                 ctx->wim->lookup_table);
        return 0;
}

#ifdef HAVE_UTIMENSAT
/*
 * Change the timestamp on a file dentry.
 *
 * Note that alternate data streams do not have their own timestamps.
 */
static int
wimfs_utimens(const char *path, const struct timespec tv[2])
{
        struct wim_inode *inode;
        WIMStruct *wim = wimfs_get_WIMStruct();

        inode = wim_pathname_to_inode(wim, path);
        if (!inode)
                return -errno;

        if (tv[0].tv_nsec != UTIME_OMIT) {
                if (tv[0].tv_nsec == UTIME_NOW)
                        inode->i_last_access_time = get_wim_timestamp();
                else
                        inode->i_last_access_time = timespec_to_wim_timestamp(tv[0]);
        }
        if (tv[1].tv_nsec != UTIME_OMIT) {
                if (tv[1].tv_nsec == UTIME_NOW)
                        inode->i_last_write_time = get_wim_timestamp();
                else
                        inode->i_last_write_time = timespec_to_wim_timestamp(tv[1]);
        }
        return 0;
}
#else /* HAVE_UTIMENSAT */
static int
wimfs_utime(const char *path, struct utimbuf *times)
{
        struct wim_inode *inode;
        WIMStruct *wim = wimfs_get_WIMStruct();

        inode = wim_pathname_to_inode(wim, path);
        if (!inode)
                return -errno;

        inode->i_last_write_time = unix_timestamp_to_wim(times->modtime);
        inode->i_last_access_time = unix_timestamp_to_wim(times->actime);
        return 0;
}
#endif /* !HAVE_UTIMENSAT */

/* Writes to a file in the WIM filesystem.
 * It may be an alternate data stream, but here we don't even notice because we
 * just get a lookup table entry. */
static int
wimfs_write(const char *path, const char *buf, size_t size,
            off_t offset, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = (struct wimfs_fd*)(uintptr_t)fi->fh;
        int ret;

        if (!fd)
                return -EBADF;

        wimlib_assert(fd->f_lte != NULL);
        wimlib_assert(fd->f_lte->staging_file_name != NULL);
        wimlib_assert(filedes_valid(&fd->staging_fd));
        wimlib_assert(fd->f_inode != NULL);

        /* Write the data. */
        ret = raw_pwrite(&fd->staging_fd, buf, size, offset);
        if (ret == -1)
                return -errno;

        /* Update file size */
        if (offset + size > fd->f_lte->size) {
                DEBUG("Update file size %"PRIu64 " => %"PRIu64"",
                      fd->f_lte->size, offset + size);
                fd->f_lte->size = offset + size;
        }

        /* Update timestamps */
        touch_inode(fd->f_inode);
        return ret;
}

static struct fuse_operations wimfs_operations = {
        .chmod       = wimfs_chmod,
        .chown       = wimfs_chown,
        .destroy     = wimfs_destroy,
        .fgetattr    = wimfs_fgetattr,
        .ftruncate   = wimfs_ftruncate,
        .getattr     = wimfs_getattr,
#ifdef ENABLE_XATTR
        .getxattr    = wimfs_getxattr,
#endif
        .link        = wimfs_link,
#ifdef ENABLE_XATTR
        .listxattr   = wimfs_listxattr,
#endif
        .mkdir       = wimfs_mkdir,
        .mknod       = wimfs_mknod,
        .open        = wimfs_open,
        .opendir     = wimfs_opendir,
        .read        = wimfs_read,
        .readdir     = wimfs_readdir,
        .readlink    = wimfs_readlink,
        .release     = wimfs_release,
        .releasedir  = wimfs_releasedir,
#ifdef ENABLE_XATTR
        .removexattr = wimfs_removexattr,
#endif
        .rename      = wimfs_rename,
        .rmdir       = wimfs_rmdir,
#ifdef ENABLE_XATTR
        .setxattr    = wimfs_setxattr,
#endif
        .symlink     = wimfs_symlink,
        .truncate    = wimfs_truncate,
        .unlink      = wimfs_unlink,
#ifdef HAVE_UTIMENSAT
        .utimens     = wimfs_utimens,
#else
        .utime       = wimfs_utime,
#endif
        .write       = wimfs_write,

        /* wimfs keeps file descriptor structures (struct wimfs_fd), so there is
         * no need to have the file path provided on operations such as read()
         * where only the file descriptor is needed. */
#if FUSE_MAJOR_VERSION > 2 || (FUSE_MAJOR_VERSION == 2 && FUSE_MINOR_VERSION >= 8)
        .flag_nullpath_ok = 1,
#endif
#if FUSE_MAJOR_VERSION > 2 || (FUSE_MAJOR_VERSION == 2 && FUSE_MINOR_VERSION >= 9)
        .flag_nopath = 1,
        .flag_utime_omit_ok = 1,
#endif
};


/* API function documented in wimlib.h  */
WIMLIBAPI int
wimlib_mount_image(WIMStruct *wim, int image, const char *dir,
                   int mount_flags, const char *staging_dir)
{
        int argc;
        char *argv[16];
        int ret;
        char *dir_copy;
        struct wim_image_metadata *imd;
        struct wimfs_context ctx;
        struct wim_inode *inode;

        DEBUG("Mount: wim = %p, image = %d, dir = %s, flags = %d, ",
              wim, image, dir, mount_flags);

        if (!wim || !dir)
                return WIMLIB_ERR_INVALID_PARAM;

        if (mount_flags & ~(WIMLIB_MOUNT_FLAG_READWRITE |
                            WIMLIB_MOUNT_FLAG_DEBUG |
                            WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_NONE |
                            WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR |
                            WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS |
                            WIMLIB_MOUNT_FLAG_UNIX_DATA |
                            WIMLIB_MOUNT_FLAG_ALLOW_OTHER))
                return WIMLIB_ERR_INVALID_PARAM;

        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                ret = can_delete_from_wim(wim);
                if (ret)
                        return ret;
        }

        ret = select_wim_image(wim, image);
        if (ret)
                return ret;

        DEBUG("Selected image %d", image);

        imd = wim_get_current_image_metadata(wim);

        if (imd->modified) {
                /* wimfs_read() only supports a limited number of stream
                 * locations, not including RESOURCE_IN_FILE_ON_DISK,
                 * RESOURCE_IN_NTFS_VOLUME, etc. that might appear if files were
                 * added to the WIM image.  */
                ERROR("Cannot mount an image with newly added files!");
                return WIMLIB_ERR_INVALID_PARAM;
        }

        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                ret = lock_wim(wim, wim->in_fd.fd);
                if (ret)
                        return ret;
        }

        /* Use default stream interface if one was not specified */
        if (!(mount_flags & (WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_NONE |
                       WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR |
                       WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS)))
                mount_flags |= WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_XATTR;

        DEBUG("Initializing struct wimfs_context");
        init_wimfs_context(&ctx);
        ctx.wim = wim;
        ctx.mount_flags = mount_flags;
        ctx.image_inode_list = &imd->inode_list;
        ctx.default_uid = getuid();
        ctx.default_gid = getgid();
        wimlib_assert(list_empty(&imd->unhashed_streams));
        if (mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS)
                ctx.default_lookup_flags = LOOKUP_FLAG_ADS_OK;

        DEBUG("Unlinking message queues in case they already exist");
        ret = set_message_queue_names(&ctx, dir);
        if (ret)
                goto out_unlock;
        unlink_message_queues(&ctx);

        DEBUG("Preparing arguments to fuse_main()");

        dir_copy = STRDUP(dir);
        if (!dir_copy) {
                ret = WIMLIB_ERR_NOMEM;
                goto out_free_message_queue_names;
        }

        argc = 0;
        argv[argc++] = "wimlib";
        argv[argc++] = dir_copy;

        /* disable multi-threaded operation */
        argv[argc++] = "-s";

        if (mount_flags & WIMLIB_MOUNT_FLAG_DEBUG)
                argv[argc++] = "-d";

        /*
         * We provide the use_ino option to the FUSE mount because we are going
         * to assign inode numbers ourselves. */
        char optstring[256] =
                "use_ino"
                ",subtype=wimfs"
                ",attr_timeout=0"
#if FUSE_MAJOR_VERSION > 2 || (FUSE_MAJOR_VERSION == 2 && FUSE_MINOR_VERSION >= 8)
                ",hard_remove"
#endif
                ",default_permissions"
                ;
        argv[argc++] = "-o";
        argv[argc++] = optstring;
        if ((mount_flags & WIMLIB_MOUNT_FLAG_READWRITE)) {
                /* Read-write mount.  Make the staging directory */
                ret = make_staging_dir(&ctx, staging_dir);
                if (ret)
                        goto out_free_dir_copy;
        } else {
                /* Read-only mount */
                strcat(optstring, ",ro");
        }
        if (mount_flags & WIMLIB_MOUNT_FLAG_ALLOW_OTHER)
                strcat(optstring, ",allow_other");
        argv[argc] = NULL;

#ifdef ENABLE_DEBUG
        {
                int i;
                DEBUG("FUSE command line (argc = %d): ", argc);
                for (i = 0; i < argc; i++) {
                        fputs(argv[i], stdout);
                        putchar(' ');
                }
                putchar('\n');
                fflush(stdout);
        }
#endif

        /* Assign inode numbers.  Also, if a read-write mount was requested,
         * mark the dentry tree as modified, and add each stream referenced by
         * files in the image to a list and preemptively double the number of
         * references to each.  The latter is done to allow implementing the
         * WIMLIB_UNMOUNT_FLAG_NEW_IMAGE semantics.  */
        ctx.next_ino = 1;
        INIT_LIST_HEAD(&ctx.orig_stream_list);
        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                imd->modified = 1;
                image_for_each_inode(inode, imd) {
                        inode->i_ino = ctx.next_ino++;
                        for (unsigned i = 0; i <= inode->i_num_ads; i++) {
                                struct wim_lookup_table_entry *lte;

                                lte = inode_stream_lte(inode, i, wim->lookup_table);
                                if (lte)
                                        lte->out_refcnt = 0;
                        }
                }
                image_for_each_inode(inode, imd) {
                        for (unsigned i = 0; i <= inode->i_num_ads; i++) {
                                struct wim_lookup_table_entry *lte;

                                lte = inode_stream_lte(inode, i,
                                                       wim->lookup_table);
                                if (lte) {
                                        if (lte->out_refcnt == 0)
                                                list_add(&lte->orig_stream_list,
                                                         &ctx.orig_stream_list);
                                        lte->out_refcnt += inode->i_nlink;
                                        lte->refcnt += inode->i_nlink;
                                }
                        }
                }
        } else {
                image_for_each_inode(inode, imd)
                        inode->i_ino = ctx.next_ino++;
        }

        DEBUG("(next_ino = %"PRIu64")", ctx.next_ino);

        DEBUG("Calling fuse_main()");

        ret = fuse_main(argc, argv, &wimfs_operations, &ctx);

        DEBUG("Returned from fuse_main() (ret = %d)", ret);

        if (ret) {
                ret = WIMLIB_ERR_FUSE;
        } else {
                if (ctx.have_status)
                        ret = ctx.status;
                else
                        ret = WIMLIB_ERR_TIMEOUT;
        }
        if (ctx.daemon_to_unmount_mq != (mqd_t)(-1)) {
                send_unmount_finished_msg(ctx.daemon_to_unmount_mq, ret);
                close_message_queues(&ctx);
        }

        release_extra_refcnts(&ctx);

        /* Try to delete the staging directory if a deletion wasn't yet
         * attempted due to an earlier error */
        if (ctx.staging_dir_name)
                delete_staging_dir(&ctx);
out_free_dir_copy:
        FREE(dir_copy);
out_unlock:
        wim->wim_locked = 0;
out_free_message_queue_names:
        free_message_queue_names(&ctx);
        return ret;
}

/* API function documented in wimlib.h  */
WIMLIBAPI int
wimlib_unmount_image(const char *dir, int unmount_flags,
                     wimlib_progress_func_t progress_func)
{
        int ret;
        struct wimfs_context wimfs_ctx;

        if (unmount_flags & ~(WIMLIB_UNMOUNT_FLAG_CHECK_INTEGRITY |
                              WIMLIB_UNMOUNT_FLAG_COMMIT |
                              WIMLIB_UNMOUNT_FLAG_REBUILD |
                              WIMLIB_UNMOUNT_FLAG_RECOMPRESS |
                              WIMLIB_UNMOUNT_FLAG_LAZY |
                              WIMLIB_UNMOUNT_FLAG_NEW_IMAGE))
                return WIMLIB_ERR_INVALID_PARAM;

        init_wimfs_context(&wimfs_ctx);

        ret = set_message_queue_names(&wimfs_ctx, dir);
        if (ret != 0)
                goto out;

        ret = open_message_queues(&wimfs_ctx, false);
        if (ret != 0)
                goto out_free_message_queue_names;

        ret = send_unmount_request_msg(wimfs_ctx.unmount_to_daemon_mq,
                                       unmount_flags,
                                       progress_func != NULL);
        if (ret != 0)
                goto out_close_message_queues;

        ret = execute_fusermount(dir, (unmount_flags & WIMLIB_UNMOUNT_FLAG_LAZY) != 0);
        if (ret != 0)
                goto out_close_message_queues;

        struct unmount_msg_handler_context handler_ctx = {
                .hdr = {
                        .timeout_seconds = 5,
                },
                .daemon_pid = 0,
                .progress_func = progress_func,
        };

        ret = message_loop(wimfs_ctx.daemon_to_unmount_mq,
                           &unmount_msg_handler_callbacks,
                           &handler_ctx.hdr);
        if (ret == 0)
                ret = handler_ctx.status;
out_close_message_queues:
        close_message_queues(&wimfs_ctx);
out_free_message_queue_names:
        free_message_queue_names(&wimfs_ctx);
out:
        return ret;
}

#else /* WITH_FUSE */


static int
mount_unsupported_error(void)
{
#if defined(__WIN32__)
        ERROR("Sorry-- Mounting WIM images is not supported on Windows!");
#else
        ERROR("wimlib was compiled with --without-fuse, which disables support "
              "for mounting WIMs.");
#endif
        return WIMLIB_ERR_UNSUPPORTED;
}

WIMLIBAPI int
wimlib_unmount_image(const tchar *dir, int unmount_flags,
                     wimlib_progress_func_t progress_func)
{
        return mount_unsupported_error();
}

WIMLIBAPI int
wimlib_mount_image(WIMStruct *wim, int image, const tchar *dir,
                   int mount_flags, const tchar *staging_dir)
{
        return mount_unsupported_error();
}

#endif /* !WITH_FUSE */