Add a clang-format file

[wimlib] / src / mount_image.c

/*
 * mount_image.c
 *
 * This file implements mounting of WIM images using FUSE
 * (Filesystem in Userspace).  See https://github.com/libfuse/libfuse
 *
 * Currently it is only expected to work on Linux.
 */

/*
 * Copyright 2012-2023 Eric Biggers
 *
 * This file is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 3 of the License, or (at your option) any
 * later version.
 *
 * This file 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 Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this file; if not, see https://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 Windows!  Please configure --without-fuse"
#endif

#define FUSE_USE_VERSION 30

#include <sys/types.h> /* sometimes required before <sys/xattr.h> */
#include <sys/xattr.h>
#include <dirent.h>
#include <errno.h>
#include <fuse.h>
#include <limits.h>
#include <mqueue.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#include <utime.h>

#include "wimlib/blob_table.h"
#include "wimlib/dentry.h"
#include "wimlib/encoding.h"
#include "wimlib/metadata.h"
#include "wimlib/paths.h"
#include "wimlib/progress.h"
#include "wimlib/reparse.h"
#include "wimlib/threads.h"
#include "wimlib/timestamp.h"
#include "wimlib/unix_data.h"
#include "wimlib/write.h"
#include "wimlib/xml.h"

#ifndef O_NOFOLLOW
#  define O_NOFOLLOW 0  /* Security only...  */
#endif

#ifndef ENOATTR
#  define ENOATTR ENODATA
#endif

#define WIMFS_MQUEUE_NAME_LEN 32

#define WIMLIB_UNMOUNT_FLAG_SEND_PROGRESS 0x80000000

struct wimfs_unmount_info {
        unsigned unmount_flags;
        char mq_name[WIMFS_MQUEUE_NAME_LEN + 1];
};

struct commit_progress_report {
        enum wimlib_progress_msg msg;
        union wimlib_progress_info info;
};

/* Description of an open file on a mounted WIM image.  Actually, this
 * represents the open state of a particular data stream of an inode, rather
 * than the inode itself.  (An inode might have multiple named data streams in
 * addition to the default, unnamed data stream.)  At a given time, an inode in
 * the WIM image might have multiple file descriptors open to it, each to any
 * one of its data streams.  */
struct wimfs_fd {

        /* Pointer to the inode of this open file.
         * 'i_num_opened_fds' of the inode tracks the number of file descriptors
         * that reference it.  */
        struct wim_inode *f_inode;

        /* Pointer to the blob descriptor for the data stream that has been
         * opened.  'num_opened_fds' of the blob descriptor tracks the number of
         * file descriptors that reference it.  Or, this value may be NULL,
         * which indicates that the opened stream is empty and consequently does
         * not have a blob descriptor.  */
        struct blob_descriptor *f_blob;

        /* If valid (filedes_valid(&f_staging_fd)), this contains the
         * corresponding native file descriptor for the staging file that has
         * been created for reading from and/or writing to this open stream.  A
         * single staging file might have multiple file descriptors open to it
         * simultaneously, each used by a different 'struct wimfs_fd'.
         *
         * Or, if invalid (!filedes_valid(&f_staging_fd)), this 'struct
         * wimfs_fd' is not associated with a staging file.  This is permissible
         * only if this 'struct wimfs_fd' was opened read-only and the stream
         * has not yet been extracted to a staging file.  */
        struct filedes f_staging_fd;

        /* 0-based index of this file descriptor in the file descriptor table of
         * its inode.  */
        u16 f_idx;

        /* Unique ID of the opened stream in the inode.  This will stay the same
         * even if the indices of the inode's streams are changed by a deletion.
         */
        u32 f_stream_id;
};

#define WIMFS_FD(fi) ((struct wimfs_fd *)(uintptr_t)((fi)->fh))

/* Context structure for a mounted WIM image.  */
struct wimfs_context {
        /* The WIMStruct containing the mounted image.  The mounted image is the
         * currently selected image (wim->current_image).  */
        WIMStruct *wim;

        /* Flags passed to wimlib_mount_image() (WIMLIB_MOUNT_FLAG_*).  */
        int mount_flags;

        /* Default flags for path lookup in the WIM image.  */
        int default_lookup_flags;

        /* Information about the user who has mounted the WIM image  */
        uid_t owner_uid;
        gid_t owner_gid;

        /* Absolute path to the mountpoint directory (may be needed for absolute
         * symbolic link fixups)  */
        char *mountpoint_abspath;
        size_t mountpoint_abspath_nchars;

        /* Information about the staging directory for a read-write mount.  */
        int parent_dir_fd;
        int staging_dir_fd;
        char *staging_dir_name;

        /* For read-write mounts, the inode number to be assigned to the next
         * created file.  Note: since this isn't a persistent filesystem and we
         * can re-assign the inode numbers just before mounting the image, it's
         * good enough to just generate inode numbers sequentially.  */
        u64 next_ino;

        /* Number of file descriptors open to the mounted WIM image.  */
        unsigned long num_open_fds;

        /* For read-write mounts, the original metadata resource of the mounted
         * image.  */
        struct blob_descriptor *metadata_resource;

        /* Parameters for unmounting the image (can be set via extended
         * attribute "wimfs.unmount_info").  */
        struct wimfs_unmount_info unmount_info;
};

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

/* Retrieve the context structure for the currently mounted WIM image.
 *
 * Note: this is a per-thread variable.  It is possible for different threads to
 * mount different images at the same time in the same process, although they
 * must use different WIMStructs!  */
static inline struct wimfs_context *
wimfs_get_context(void)
{
        return WIMFS_CTX(fuse_get_context());
}

static void
wimfs_inc_num_open_fds(void)
{
        wimfs_get_context()->num_open_fds++;
}

static void
wimfs_dec_num_open_fds(void)
{
        wimfs_get_context()->num_open_fds--;
}

/* Retrieve the WIMStruct for the currently mounted WIM image.  */
static inline WIMStruct *
wimfs_get_WIMStruct(void)
{
        return wimfs_get_context()->wim;
}

/* Is write permission requested on the file?  */
static inline bool
flags_writable(int open_flags)
{
        int accmode = (open_flags & O_ACCMODE);
        return (accmode == O_RDWR || accmode == O_WRONLY);
}

static mode_t
fuse_mask_mode(mode_t mode, const struct fuse_context *fuse_ctx)
{
        return mode & ~fuse_ctx->umask;
}

/*
 * Allocate a file descriptor to a data stream in the mounted WIM image.
 *
 * @inode
 *      The inode containing the stream being opened
 * @strm
 *      The stream of the inode being opened
 * @fd_ret
 *      On success, a pointer to the new file descriptor will be stored here.
 *
 * Returns 0 or a -errno code.
 */
static int
alloc_wimfs_fd(struct wim_inode *inode,
               struct wim_inode_stream *strm,
               struct wimfs_fd **fd_ret)
{
        static const u16 min_fds_per_alloc = 8;
        static const u16 max_fds = 0xffff;
        u16 i;
        struct wimfs_fd *fd;

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

                /* Expand this inode's file descriptor table.  */

                num_new_fds = max(min_fds_per_alloc,
                                  inode->i_num_allocated_fds / 4);

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

                if (num_new_fds == 0)
                        return -EMFILE;

                fds = REALLOC(inode->i_fds,
                              (inode->i_num_allocated_fds + num_new_fds) *
                                sizeof(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;
                inode->i_next_fd = inode->i_num_opened_fds;
        }

        /* Allocate the file descriptor in the first available space in the
         * inode's file descriptor table.
         *
         * i_next_fd is the lower bound on the next open slot.  */
        for (i = inode->i_next_fd; inode->i_fds[i]; i++)
                ;

        fd = MALLOC(sizeof(*fd));
        if (!fd)
                return -ENOMEM;

        fd->f_inode     = inode;
        fd->f_blob      = stream_blob_resolved(strm);
        filedes_invalidate(&fd->f_staging_fd);
        fd->f_idx       = i;
        fd->f_stream_id = strm->stream_id;
        *fd_ret         = fd;
        inode->i_fds[i] = fd;
        inode->i_num_opened_fds++;
        if (fd->f_blob)
                fd->f_blob->num_opened_fds++;
        wimfs_inc_num_open_fds();
        inode->i_next_fd = i + 1;
        return 0;
}

/*
 * Close a file descriptor to a data stream in the mounted WIM image.
 *
 * Returns 0 or a -errno code.  The file descriptor is always closed.
 */
static int
close_wimfs_fd(struct wimfs_fd *fd)
{
        int ret = 0;
        struct wim_inode *inode;

        /* Close the staging file if open.  */
        if (filedes_valid(&fd->f_staging_fd))
                 if (filedes_close(&fd->f_staging_fd))
                         ret = -errno;

        /* Release this file descriptor from its blob descriptor.  */
        if (fd->f_blob)
                blob_decrement_num_opened_fds(fd->f_blob);

        wimfs_dec_num_open_fds();

        /* Release this file descriptor from its inode.  */
        inode = fd->f_inode;
        inode->i_fds[fd->f_idx] = NULL;
        if (fd->f_idx < inode->i_next_fd)
                inode->i_next_fd = fd->f_idx;
        FREE(fd);
        inode_dec_num_opened_fds(inode);
        return ret;
}

/*
 * Translate a path into the corresponding inode in the mounted WIM image.
 *
 * See get_dentry() for more information.
 *
 * Returns a pointer to the resulting inode, or NULL with errno set.
 */
static struct wim_inode *
wim_pathname_to_inode(WIMStruct *wim, const char *path)
{
        struct wim_dentry *dentry;

        dentry = get_dentry(wim, path, WIMLIB_CASE_SENSITIVE);
        if (!dentry)
                return NULL;
        return dentry->d_inode;
}

/* Can look up named data stream with colon syntax  */
#define LOOKUP_FLAG_ADS_OK              0x01

/* Can look up directory (otherwise get -ENOTDIR)  */
#define LOOKUP_FLAG_DIRECTORY_OK        0x02

/* Get the data stream of the specified name from the specified inode.  Returns
 * NULL with errno set if not found.  */
static struct wim_inode_stream *
inode_get_data_stream_tstr(const struct wim_inode *inode,
                           const char *stream_name)
{
        struct wim_inode_stream *strm;

        if (!stream_name || !*stream_name) {
                strm = inode_get_unnamed_data_stream(inode);
        } else {
                const utf16lechar *uname;

                if (tstr_get_utf16le(stream_name, &uname))
                        return NULL;
                strm = inode_get_stream(inode, STREAM_TYPE_DATA, uname);
                tstr_put_utf16le(uname);
        }
        if (!strm)
                errno = ENOENT;
        return strm;
}

/*
 * Translate a path into the corresponding dentry and stream in the mounted WIM
 * image.
 *
 * Returns 0 or a -errno code.  @dentry_ret and @strm_ret are both optional.
 */
static int
wim_pathname_to_stream(const struct wimfs_context *ctx,
                       const char *path,
                       int lookup_flags,
                       struct wim_dentry **dentry_ret,
                       struct wim_inode_stream **strm_ret)
{
        WIMStruct *wim = ctx->wim;
        struct wim_dentry *dentry;
        struct wim_inode *inode;
        struct wim_inode_stream *strm;
        const char *stream_name = NULL;
        char *p = NULL;

        lookup_flags |= ctx->default_lookup_flags;

        if (lookup_flags & LOOKUP_FLAG_ADS_OK) {
                stream_name = path_stream_name(path);
                if (stream_name) {
                        p = (char *)stream_name - 1;
                        *p = '\0';
                }
        }

        dentry = get_dentry(wim, path, WIMLIB_CASE_SENSITIVE);
        if (p)
                *p = ':';
        if (!dentry)
                return -errno;

        inode = dentry->d_inode;

        if (inode_resolve_streams(inode, wim->blob_table, false))
                return -EIO;

        if (!(lookup_flags & LOOKUP_FLAG_DIRECTORY_OK)
              && inode_is_directory(inode))
                return -EISDIR;

        strm = inode_get_data_stream_tstr(inode, stream_name);
        if (!strm) {
                /* Force creation of an unnamed data stream  */
                if (!stream_name)
                        strm = inode_add_stream(inode, STREAM_TYPE_DATA,
                                                NO_STREAM_NAME, NULL);
                if (!strm)
                        return -errno;
        }

        if (dentry_ret)
                *dentry_ret = dentry;
        if (strm_ret)
                *strm_ret = strm;
        return 0;
}

/*
 * Create a new file in the mounted WIM image.
 *
 * @fuse_ctx
 *      The FUSE context for the mounted image.
 * @path
 *      The path at which to create the first link to the new file.  If a file
 *      already exists at this path, -EEXIST is returned.
 * @mode
 *      The UNIX mode for the new file.  This is only fully honored if
 *      WIMLIB_MOUNT_FLAG_UNIX_DATA was passed to wimlib_mount_image().
 * @rdev
 *      The device ID for the new file, encoding the major and minor device
 *      numbers.  This is only honored if WIMLIB_MOUNT_FLAG_UNIX_DATA was passed
 *      to wimlib_mount_image().
 * @dentry_ret
 *      On success, a pointer to the new dentry is returned here.  Its d_inode
 *      member will point to the new inode that was created for it and added to
 *      the mounted WIM image.
 *
 * Returns 0 or a -errno code.
 */
static int
create_file(struct fuse_context *fuse_ctx, const char *path,
            mode_t mode, dev_t rdev, struct wim_dentry **dentry_ret)
{
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);
        struct wim_dentry *parent;
        const char *basename;
        struct wim_dentry *dentry;
        struct wim_inode *inode;

        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;

        if (new_dentry_with_new_inode(basename, true, &dentry))
                return -ENOMEM;

        inode = dentry->d_inode;

        inode->i_ino = wimfs_ctx->next_ino++;

        /* Note: we still use FILE_ATTRIBUTE_NORMAL for device nodes, named
         * pipes, and sockets.  The real mode is in the UNIX metadata.  */
        if (S_ISDIR(mode))
                inode->i_attributes = FILE_ATTRIBUTE_DIRECTORY;
        else
                inode->i_attributes = FILE_ATTRIBUTE_NORMAL;

        if (wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA) {
                struct wimlib_unix_data unix_data;

                unix_data.uid = fuse_ctx->uid;
                unix_data.gid = fuse_ctx->gid;
                unix_data.mode = fuse_mask_mode(mode, fuse_ctx);
                unix_data.rdev = rdev;
                if (!inode_set_unix_data(inode, &unix_data, UNIX_DATA_ALL))
                {
                        free_dentry(dentry);
                        return -ENOMEM;
                }
        }

        hlist_add_head(&inode->i_hlist_node,
                       &wim_get_current_image_metadata(wimfs_ctx->wim)->inode_list);

        dentry_add_child(parent, dentry);

        *dentry_ret = dentry;
        return 0;
}

/*
 * Remove a dentry from the mounted WIM image; i.e. remove an alias for an
 * inode.
 */
static void
remove_dentry(struct wim_dentry *dentry, struct blob_table *blob_table)
{
        /* Drop blob references.  */
        inode_unref_blobs(dentry->d_inode, blob_table);

        /* Unlink the dentry from the image's dentry tree.  */
        unlink_dentry(dentry);

        /* Delete the dentry.  This will also decrement the link count of the
         * corresponding inode, and possibly cause it to be deleted as well.  */
        free_dentry(dentry);
}

/* Generate UNIX filetype mode bits for the specified WIM inode, based on its
 * Windows file attributes.  */
static mode_t
inode_unix_file_type(const struct wim_inode *inode)
{
        if (inode_is_symlink(inode))
                return S_IFLNK;
        else if (inode_is_directory(inode))
                return S_IFDIR;
        else
                return S_IFREG;
}

/* Generate a default UNIX mode for the specified WIM inode.  */
static mode_t
inode_default_unix_mode(const struct wim_inode *inode)
{
        return inode_unix_file_type(inode) | 0777;
}

static u64
blob_size(const struct blob_descriptor *blob)
{
        if (!blob)
                return 0;
        return blob->size;
}

static u64
blob_stored_size(const struct blob_descriptor *blob)
{
        if (!blob)
                return 0;
        if (blob->blob_location == BLOB_IN_WIM &&
            blob->size == blob->rdesc->uncompressed_size)
                return blob->rdesc->size_in_wim;
        return blob->size;
}

/*
 * Retrieve standard UNIX metadata ('struct stat') for a WIM inode.
 *
 * @blob is the blob descriptor for the stream of the inode that is being
 * queried, or NULL.  We mostly return the same information for all streams, but
 * st_size and st_blocks may be different for different streams.
 *
 * This always returns 0.
 */
static int
inode_to_stbuf(const struct wim_inode *inode,
               const struct blob_descriptor *blob, struct stat *stbuf)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        struct wimlib_unix_data unix_data;

        memset(stbuf, 0, sizeof(struct stat));
        if ((ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA) &&
            inode_get_unix_data(inode, &unix_data))
        {
                /* Use the user ID, group ID, mode, and device ID from the
                 * inode's extra UNIX metadata information.  */
                stbuf->st_uid = unix_data.uid;
                stbuf->st_gid = unix_data.gid;
                stbuf->st_mode = unix_data.mode;
                stbuf->st_rdev = unix_data.rdev;
        } else {
                /* Generate default values for the user ID, group ID, and mode.
                 *
                 * Note: in the case of an allow_other mount, fuse_context.uid
                 * may not be the same as wimfs_context.owner_uid!  */
                stbuf->st_uid = ctx->owner_uid;
                stbuf->st_gid = ctx->owner_gid;
                stbuf->st_mode = inode_default_unix_mode(inode);
        }
        stbuf->st_ino = inode->i_ino;
        stbuf->st_nlink = inode->i_nlink;
        stbuf->st_size = blob_size(blob);
#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_time_t(inode->i_last_access_time);
        stbuf->st_mtime = wim_timestamp_to_time_t(inode->i_last_write_time);
        stbuf->st_ctime = stbuf->st_mtime;
#endif
        stbuf->st_blocks = DIV_ROUND_UP(blob_stored_size(blob), 512);
        return 0;
}

/* Update the last access and last write timestamps of a WIM inode.  */
static void
touch_inode(struct wim_inode *inode)
{
        u64 now = now_as_wim_timestamp();
        inode->i_last_access_time = now;
        inode->i_last_write_time = now;
}

static void
touch_parent(struct wim_dentry *dentry)
{
        touch_inode(dentry->d_parent->d_inode);
}

/*
 * Update inode metadata after a regular file's contents have changed:
 *
 * - Update the timestamps
 * - Clear the setuid and setgid bits
 */
static void
file_contents_changed(struct wim_inode *inode)
{
        struct wimlib_unix_data unix_data;
        bool ok;

        touch_inode(inode);

        if (inode_get_unix_data(inode, &unix_data)) {
                unix_data.mode &= ~(S_ISUID | S_ISGID);
                ok = inode_set_unix_data(inode, &unix_data, UNIX_DATA_MODE);
                /*
                 * This cannot fail because no memory allocation should have
                 * been required, as the UNIX data already exists.
                 */
                wimlib_assert(ok);
        } /* Else, set[ug]id can't be set, so there's nothing to do. */
}

/*
 * Create a new file in the staging directory for a read-write mounted image.
 *
 * On success, returns the file descriptor for the new staging file, opened for
 * writing.  In addition, stores the allocated name of the staging file in
 * @name_ret.
 *
 * On failure, returns -1 and sets errno.
 */
static int
create_staging_file(const struct wimfs_context *ctx, char **name_ret)
{

        static const size_t STAGING_FILE_NAME_LEN = 20;
        char *name;
        int fd;

        name = MALLOC(STAGING_FILE_NAME_LEN + 1);
        if (!name)
                return -1;
        name[STAGING_FILE_NAME_LEN] = '\0';

retry:
        get_random_alnum_chars(name, STAGING_FILE_NAME_LEN);
        fd = openat(ctx->staging_dir_fd, name,
                    O_WRONLY | O_CREAT | O_EXCL | O_NOFOLLOW, 0600);
        if (unlikely(fd < 0)) {
                if (unlikely(errno == EEXIST))
                        /* Try again with another name.  */
                        goto retry;
                FREE(name);
        } else {
                *name_ret = name;
        }
        return fd;
}

/*
 * Extract a blob to the staging directory.  This is necessary when a stream
 * using the blob is being opened for writing and the blob has not already been
 * extracted to the staging directory.
 *
 * @inode
 *      The inode containing the stream being opened for writing.
 * @strm
 *      The stream being opened for writing.  The blob descriptor to which the
 *      stream refers will be changed by this function.
 * @size
 *      Number of bytes of the blob to extract and include in the staging file.
 *      It may be less than the actual blob length, in which case only a prefix
 *      of the blob will be extracted.  It may also be more than the actual blob
 *      length, in which case the extra space will be zero-filled.
 *
 * Returns 0 or a -errno code.
 */
static int
extract_blob_to_staging_dir(struct wim_inode *inode,
                            struct wim_inode_stream *strm,
                            off_t size, const struct wimfs_context *ctx)
{
        struct blob_descriptor *old_blob;
        struct blob_descriptor *new_blob;
        char *staging_file_name;
        int staging_fd;
        off_t extract_size;
        int result;
        int ret;

        old_blob = stream_blob_resolved(strm);

        /* Create the staging file.  */
        staging_fd = create_staging_file(ctx, &staging_file_name);
        if (unlikely(staging_fd < 0))
                return -errno;

        /* Extract the stream to the staging file (possibly truncated).  */
        if (old_blob) {
                struct filedes fd;

                filedes_init(&fd, staging_fd);
                errno = 0;
                extract_size = min(old_blob->size, size);
                result = extract_blob_prefix_to_fd(old_blob, extract_size, &fd);
        } else {
                extract_size = 0;
                result = 0;
        }

        /* In the case of truncate() to more than the file length, extend the
         * staging file with zeroes by calling ftruncate().  */
        if (!result && size > extract_size)
                result = ftruncate(staging_fd, size);

        /* Close the staging file.  */
        if (close(staging_fd))
                result = -1;

        /* If an error occurred, unlink the staging file.  */
        if (unlikely(result)) {
                /* extract_blob_to_fd() should set errno, but if it didn't,
                 * set a default value.  */
                ret = errno ? -errno : -EIO;
                goto out_delete_staging_file;
        }

        /* Create a blob descriptor for the staging file.  */
        new_blob = new_blob_descriptor();
        if (unlikely(!new_blob)) {
                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, update them to use the
         * new blob descriptor, and open staging file descriptors for them.  */
        for (u16 i = 0, j = 0; j < inode->i_num_opened_fds; i++) {
                struct wimfs_fd *fd;
                int raw_fd;

                fd = inode->i_fds[i];
                if (!fd)
                        continue;

                j++;

                if (fd->f_stream_id != strm->stream_id)
                        continue;

                /* This is a readonly fd for the same stream.  */
                fd->f_blob = new_blob;
                new_blob->num_opened_fds++;
                raw_fd = openat(ctx->staging_dir_fd, staging_file_name,
                                O_RDONLY | O_NOFOLLOW);
                if (unlikely(raw_fd < 0)) {
                        ret = -errno;
                        goto out_revert_fd_changes;
                }
                filedes_init(&fd->f_staging_fd, raw_fd);
        }

        if (old_blob)
                old_blob->num_opened_fds -= new_blob->num_opened_fds;

        new_blob->blob_location     = BLOB_IN_STAGING_FILE;
        new_blob->staging_file_name = staging_file_name;
        new_blob->staging_dir_fd    = ctx->staging_dir_fd;
        new_blob->size              = size;

        prepare_unhashed_blob(new_blob, inode, strm->stream_id,
                              &wim_get_current_image_metadata(ctx->wim)->unhashed_blobs);
        inode_replace_stream_blob(inode, strm, new_blob, ctx->wim->blob_table);
        if (size != blob_size(old_blob))
                file_contents_changed(inode);
        return 0;

out_revert_fd_changes:
        for (u16 i = 0; new_blob->num_opened_fds; i++) {
                struct wimfs_fd *fd = inode->i_fds[i];
                if (fd && fd->f_stream_id == strm->stream_id) {
                        fd->f_blob = old_blob;
                        if (filedes_valid(&fd->f_staging_fd)) {
                                filedes_close(&fd->f_staging_fd);
                                filedes_invalidate(&fd->f_staging_fd);
                        }
                        new_blob->num_opened_fds--;
                }
        }
        free_blob_descriptor(new_blob);
out_delete_staging_file:
        unlinkat(ctx->staging_dir_fd, staging_file_name, 0);
        FREE(staging_file_name);
        return ret;
}

/*
 * Create the staging directory for the WIM file.
 *
 * The staging directory will be created in the directory specified by the open
 * file descriptor @parent_dir_fd.  It will be given a randomly generated name
 * based on @wim_basename, the name of the WIM file.
 *
 * On success, returns a file descriptor to the open staging directory with
 * O_RDONLY access.  In addition, stores the allocated name of the staging
 * directory (relative to @parent_dir_fd) in @staging_dir_name_ret.
 * On failure, returns -1 and sets errno.
 */
static int
make_staging_dir_at(int parent_dir_fd, const char *wim_basename,
                    char **staging_dir_name_ret)
{
        static const char common_suffix[8] = ".staging";
        static const size_t random_suffix_len = 10;
        size_t wim_basename_len;
        size_t staging_dir_name_len;
        char *staging_dir_name;
        char *p;
        int fd;

        wim_basename_len = strlen(wim_basename);
        staging_dir_name_len = wim_basename_len + sizeof(common_suffix) +
                               random_suffix_len;
        staging_dir_name = MALLOC(staging_dir_name_len + 1);
        if (!staging_dir_name)
                return -1;

        p = staging_dir_name;
        p = mempcpy(p, wim_basename, wim_basename_len);
        p = mempcpy(p, common_suffix, sizeof(common_suffix));
        get_random_alnum_chars(p, random_suffix_len);
        p += random_suffix_len;
        *p = '\0';

        if (mkdirat(parent_dir_fd, staging_dir_name, 0700))
                goto err1;

        fd = openat(parent_dir_fd, staging_dir_name,
                    O_RDONLY | O_DIRECTORY | O_NOFOLLOW);
        if (fd < 0)
                goto err2;

        *staging_dir_name_ret = staging_dir_name;
        return fd;

err2:
        unlinkat(parent_dir_fd, staging_dir_name, AT_REMOVEDIR);
err1:
        FREE(staging_dir_name);
        return -1;
}

/*
 * Create the staging directory and set ctx->staging_dir_fd,
 * ctx->staging_dir_name, and ctx->parent_dir_fd.
 */
static int
make_staging_dir(struct wimfs_context *ctx, const char *parent_dir_path)
{
        const char *wim_basename;
        char *end = NULL;
        int ret;

        wim_basename = path_basename(ctx->wim->filename);

        if (!parent_dir_path) {
                /* The user did not specify a directory.  Default to creating
                 * the staging directory alongside the WIM file.  */
                if (wim_basename > ctx->wim->filename) {
                        parent_dir_path = ctx->wim->filename;
                        end = (char *)(wim_basename - 1);
                        /* *end must be a slash.  Temporarily overwrite it so we
                         * can open the parent directory.  */
                        *end = '\0';
                } else {
                        parent_dir_path = ".";
                }
        }

        /* Open the parent directory (in which we'll create our staging
         * directory).  */
        ctx->parent_dir_fd = open(parent_dir_path, O_RDONLY | O_DIRECTORY);
        if (ctx->parent_dir_fd < 0) {
                ERROR_WITH_ERRNO("Can't open directory \"%s\"",
                                 parent_dir_path);
                ret = WIMLIB_ERR_OPENDIR;
                goto out_restore_wim_filename;
        }

        ctx->staging_dir_fd = make_staging_dir_at(ctx->parent_dir_fd,
                                                  wim_basename,
                                                  &ctx->staging_dir_name);
        if (ctx->staging_dir_fd < 0) {
                ERROR_WITH_ERRNO("Can't create staging directory in \"%s\"",
                                 parent_dir_path);
                close(ctx->parent_dir_fd);
                ret = WIMLIB_ERR_MKDIR;
                goto out_restore_wim_filename;
        }
        ret = 0;
out_restore_wim_filename:
        if (end)
                *end = '/';
        return ret;
}

/* Deletes the staging directory, undoing the effects of a successful call to
 * make_staging_dir().  */
static void
delete_staging_dir(struct wimfs_context *ctx)
{
        DIR *dir;
        struct dirent *ent;

        dir = fdopendir(ctx->staging_dir_fd);
        if (dir) {
                while ((ent = readdir(dir)))
                        unlinkat(ctx->staging_dir_fd, ent->d_name, 0);
                closedir(dir);
        } else {
                close(ctx->staging_dir_fd);
        }
        if (unlinkat(ctx->parent_dir_fd, ctx->staging_dir_name, AT_REMOVEDIR))
                WARNING_WITH_ERRNO("Could not delete staging directory");
        FREE(ctx->staging_dir_name);
        close(ctx->parent_dir_fd);
}

static void
prepare_inodes(struct wimfs_context *ctx)
{
        struct wim_image_metadata *imd;
        struct wim_inode *inode;

        ctx->next_ino = 1;
        imd = wim_get_current_image_metadata(ctx->wim);
        image_for_each_inode(inode, imd) {
                inode->i_ino = ctx->next_ino++;
                inode->i_num_opened_fds = 0;
                inode->i_num_allocated_fds = 0;
                inode->i_fds = NULL;
        }
}

/* Delete the 'struct blob_descriptor' for any stream that was modified
 * or created in the read-write mounted image and had a final size of 0.  */
static void
delete_empty_blobs(struct wimfs_context *ctx)
{
        struct blob_descriptor *blob, *tmp;
        struct wim_image_metadata *imd;

        imd = wim_get_current_image_metadata(ctx->wim);

        image_for_each_unhashed_blob_safe(blob, tmp, imd) {
                if (!blob->size) {
                        *retrieve_pointer_to_unhashed_blob(blob) = NULL;
                        list_del(&blob->unhashed_list);
                        free_blob_descriptor(blob);
                }
        }
}

/* Close all file descriptors open to the specified inode.
 *
 * Note: closing the last file descriptor might free the inode.  */
static void
inode_close_fds(struct wim_inode *inode)
{
        u16 num_open_fds = inode->i_num_opened_fds;
        for (u16 i = 0; num_open_fds; i++) {
                if (inode->i_fds[i]) {
                        close_wimfs_fd(inode->i_fds[i]);
                        num_open_fds--;
                }
        }
}

/* Close all file descriptors open to the mounted image.  */
static void
close_all_fds(struct wimfs_context *ctx)
{
        struct wim_inode *inode;
        struct hlist_node *tmp;
        struct wim_image_metadata *imd;

        imd = wim_get_current_image_metadata(ctx->wim);

        image_for_each_inode_safe(inode, tmp, imd)
                inode_close_fds(inode);
}

/* 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 image = wim->current_image;
        struct wim_image_metadata *imd;
        struct wim_inode *inode;
        int ret;

        ret = WIMLIB_ERR_NOMEM;
        imd = new_unloaded_image_metadata(ctx->metadata_resource);
        if (!imd)
                goto err;

        ret = append_image_metadata(wim, wim->image_metadata[image - 1]);
        if (ret)
                goto err_put_imd;

        ret = xml_export_image(wim->xml_info, image,
                               wim->xml_info, NULL, NULL, false);
        if (ret)
                goto err_undo_append;

        wim->image_metadata[image - 1] = imd;
        wim->current_image = wim->hdr.image_count;

        ret = select_wim_image(wim, image);
        if (ret)
                goto err_undo_export;

        image_for_each_inode(inode, imd) {
                for (unsigned i = 0; i < inode->i_num_streams; i++) {
                        struct blob_descriptor *blob;

                        blob = stream_blob(&inode->i_streams[i],
                                           wim->blob_table);
                        if (blob)
                                blob->refcnt += inode->i_nlink;
                }
        }

        select_wim_image(wim, wim->hdr.image_count);
        ctx->metadata_resource = NULL;
        return 0;

err_undo_export:
        xml_delete_image(wim->xml_info, wim->hdr.image_count);
        wim->image_metadata[image - 1] = wim->image_metadata[wim->hdr.image_count - 1];
        wim->current_image = image;
err_undo_append:
        wim->hdr.image_count--;
err_put_imd:
        imd->metadata_blob = NULL;
        put_image_metadata(imd);
err:
        return ret;
}

static enum wimlib_progress_status
commit_progress_func(enum wimlib_progress_msg msg,
                     union wimlib_progress_info *info, void *progctx)
{
        mqd_t mq = *(mqd_t *)progctx;
        struct commit_progress_report report;

        memset(&report, 0, sizeof(report));
        report.msg = msg;
        if (info)
                report.info = *info;
        mq_send(mq, (const char *)&report, sizeof(report), 1);
        return WIMLIB_PROGRESS_STATUS_CONTINUE;
}

/* Commit the mounted image to the underlying WIM file.  */
static int
commit_image(struct wimfs_context *ctx, int unmount_flags, mqd_t mq)
{
        int write_flags;

        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_SEND_PROGRESS)
                wimlib_register_progress_function(ctx->wim,
                                                  commit_progress_func, &mq);
        else
                wimlib_register_progress_function(ctx->wim, NULL, NULL);

        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_NEW_IMAGE) {
                int ret = renew_current_image(ctx);
                if (ret)
                        return ret;
        }
        delete_empty_blobs(ctx);

        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;

        return wimlib_overwrite(ctx->wim, write_flags, 0);
}

/* In the case of an allow_other mount, only the mount owner and root are
 * allowed to unmount the filesystem.  */
static bool
may_unmount_wimfs(void)
{
        const struct fuse_context *fuse_ctx = fuse_get_context();
        const struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);

        return (fuse_ctx->uid == wimfs_ctx->owner_uid ||
                fuse_ctx->uid == 0);
}

/* Unmount the mounted image, called from the daemon process.  */
static int
unmount_wimfs(void)
{
        struct fuse_context *fuse_ctx = fuse_get_context();
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);
        const struct wimfs_unmount_info *info = &wimfs_ctx->unmount_info;
        int unmount_flags = info->unmount_flags;
        mqd_t mq = (mqd_t)-1;
        int ret;

        /* Ignore COMMIT if the image is mounted read-only.  */
        if (!(wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_READWRITE))
                unmount_flags &= ~WIMLIB_UNMOUNT_FLAG_COMMIT;

        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_SEND_PROGRESS) {
                mq = mq_open(info->mq_name, O_WRONLY | O_NONBLOCK);
                if (mq == (mqd_t)-1) {
                        ret = WIMLIB_ERR_MQUEUE;
                        goto out;
                }
        }

        if (wimfs_ctx->num_open_fds) {

                /* There are still open file descriptors to the image.  */

                /* With COMMIT, refuse to unmount unless FORCE is also
                 * specified.  */
                if ((unmount_flags & (WIMLIB_UNMOUNT_FLAG_COMMIT |
                                      WIMLIB_UNMOUNT_FLAG_FORCE))
                                 == WIMLIB_UNMOUNT_FLAG_COMMIT)
                {
                        ret = WIMLIB_ERR_MOUNTED_IMAGE_IS_BUSY;
                        goto out;
                }

                /* Force-close all file descriptors.  */
                close_all_fds(wimfs_ctx);
        }

        if (unmount_flags & WIMLIB_UNMOUNT_FLAG_COMMIT)
                ret = commit_image(wimfs_ctx, unmount_flags, mq);
        else
                ret = 0;  /* Read-only mount, or discarding changes to
                             a read-write mount  */

out:
        /* Leave the image mounted if commit failed, unless this is a
         * forced unmount.  The user can retry without COMMIT if they
         * want.  */
        if (!ret || (unmount_flags & WIMLIB_UNMOUNT_FLAG_FORCE)) {
                unlock_wim_for_append(wimfs_ctx->wim);
                fuse_exit(fuse_ctx->fuse);
        }
        if (mq != (mqd_t)-1)
                mq_close(mq);
        return ret;
}

static void *
wimfs_init(struct fuse_conn_info *conn, struct fuse_config *cfg)
{
        /*
         * Cache positive name lookups indefinitely, since names can only be
         * added, removed, or modified through the mounted filesystem itself.
         */
        cfg->entry_timeout = 1000000000;

        /*
         * Cache negative name lookups indefinitely, since names can only be
         * added, removed, or modified through the mounted filesystem itself.
         */
        cfg->negative_timeout = 1000000000;

        /*
         * Don't cache file/directory attributes.  This is needed as a
         * workaround for the fact that when caching attributes, the high level
         * interface to libfuse considers a file which has several hard-linked
         * names as several different files.  (Otherwise, we could cache our
         * file/directory attributes indefinitely, since they can only be
         * changed through the mounted filesystem itself.)
         */
        cfg->attr_timeout = 0;

        /*
         * If an open file is unlinked, unlink it for real rather than renaming
         * it to a hidden file.  Our code supports this; an unlinked inode is
         * retained until all its file descriptors have been closed.
         */
        cfg->hard_remove = 1;

        /*
         * Make FUSE use the inode numbers we provide.  We want this, because we
         * have inodes and will number them ourselves.
         */
        cfg->use_ino = 1;

        /*
         * Cache the contents of files.  This will speed up repeated access to
         * files on a mounted WIM image, since they won't need to be
         * decompressed repeatedly.  This option is valid because data in the
         * WIM image should never be changed externally.  (Although, if someone
         * really wanted to they could modify the WIM file or mess with the
         * staging directory; but then they're asking for trouble.)
         */
        cfg->kernel_cache = 1;

        /*
         * We keep track of file descriptor structures (struct wimfs_fd), so
         * there is no need to have the file path provided on operations such as
         * read().
         */
        cfg->nullpath_ok = 1;

        return wimfs_get_context();
}

static int
wimfs_chmod(const char *path, mode_t mask, struct fuse_file_info *fi)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        struct wim_inode *inode;
        struct wimlib_unix_data unix_data;

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

        if (fi) {
                inode = WIMFS_FD(fi)->f_inode;
        } else {
                inode = wim_pathname_to_inode(ctx->wim, path);
                if (!inode)
                        return -errno;
        }
        unix_data.uid = ctx->owner_uid;
        unix_data.gid = ctx->owner_gid;
        unix_data.mode = mask;
        unix_data.rdev = 0;

        if (!inode_set_unix_data(inode, &unix_data, UNIX_DATA_MODE))
                return -ENOMEM;

        return 0;
}

static int
wimfs_chown(const char *path, uid_t uid, gid_t gid, struct fuse_file_info *fi)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        struct wim_inode *inode;
        struct wimlib_unix_data unix_data;
        int which;

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

        if (fi) {
                inode = WIMFS_FD(fi)->f_inode;
        } else {
                inode = wim_pathname_to_inode(ctx->wim, path);
                if (!inode)
                        return -errno;
        }

        which = 0;

        if (uid != (uid_t)-1)
                which |= UNIX_DATA_UID;
        else
                uid = ctx->owner_uid;

        if (gid != (gid_t)-1)
                which |= UNIX_DATA_GID;
        else
                gid = ctx->owner_gid;

        unix_data.uid = uid;
        unix_data.gid = gid;
        unix_data.mode = inode_default_unix_mode(inode);
        unix_data.rdev = 0;

        if (!inode_set_unix_data(inode, &unix_data, which))
                return -ENOMEM;

        return 0;
}

static int
wimfs_getattr(const char *path, struct stat *stbuf, struct fuse_file_info *fi)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        const struct wim_inode *inode;
        const struct blob_descriptor *blob;
        int ret;

        if (fi) {
                const struct wimfs_fd *fd = WIMFS_FD(fi);

                inode = fd->f_inode;
                blob = fd->f_blob;
        } else {
                struct wim_dentry *dentry;
                struct wim_inode_stream *strm;

                ret = wim_pathname_to_stream(ctx, path,
                                             LOOKUP_FLAG_DIRECTORY_OK,
                                             &dentry, &strm);
                if (ret)
                        return ret;
                inode = dentry->d_inode;
                blob = stream_blob_resolved(strm);
        }

        return inode_to_stbuf(inode, blob, stbuf);
}

static int
copy_xattr(char *dest, size_t destsize, const void *src, size_t srcsize)
{
        if (destsize) {
                if (destsize < srcsize)
                        return -ERANGE;
                memcpy(dest, src, srcsize);
        }
        return srcsize;
}

static int
wimfs_getxattr(const char *path, const char *name, char *value,
               size_t size)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        const struct wim_inode *inode;
        const struct wim_inode_stream *strm;
        const struct blob_descriptor *blob;

        if (!strncmp(name, "wimfs.", 6)) {
                /* Handle some magical extended attributes.  These really should
                 * be ioctls, but directory ioctls aren't supported until
                 * libfuse 2.9, and even then they are broken.  */
                name += 6;
                if (!strcmp(name, "wim_filename")) {
                        return copy_xattr(value, size, ctx->wim->filename,
                                          strlen(ctx->wim->filename));
                }
                if (!strcmp(name, "wim_info")) {
                        struct wimlib_wim_info info;

                        wimlib_get_wim_info(ctx->wim, &info);

                        return copy_xattr(value, size, &info, sizeof(info));
                }
                if (!strcmp(name, "mounted_image")) {
                        return copy_xattr(value, size,
                                          &ctx->wim->current_image, sizeof(int));
                }
                if (!strcmp(name, "mount_flags")) {
                        return copy_xattr(value, size,
                                          &ctx->mount_flags, sizeof(int));
                }
                if (!strcmp(name, "unmount")) {
                        if (!may_unmount_wimfs())
                                return -EPERM;
                        if (size) {
                                int status;

                                if (size < sizeof(int))
                                        return -ERANGE;
                                status = unmount_wimfs();
                                memcpy(value, &status, sizeof(int));
                        }
                        return sizeof(int);
                }
                return -ENOATTR;
        }

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

        if (strncmp(name, "user.", 5))
                return -ENOATTR;
        name += 5;

        if (!*name)
                return -ENOATTR;

        /* Querying a named data stream  */

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

        strm = inode_get_data_stream_tstr(inode, name);
        if (!strm)
                return (errno == ENOENT) ? -ENOATTR : -errno;

        blob = stream_blob_resolved(strm);
        if (!blob)
                return 0;

        if (unlikely(blob->size > INT_MAX))
                return -EFBIG;

        if (size) {
                if (size < blob->size)
                        return -ERANGE;

                if (read_blob_into_buf(blob, value))
                        return errno ? -errno : -EIO;
        }
        return blob->size;
}

static int
wimfs_link(const char *existing_path, const char *new_path)
{
        WIMStruct *wim = wimfs_get_WIMStruct();
        const char *new_name;
        struct wim_inode *inode;
        struct wim_dentry *dir;
        struct wim_dentry *new_alias;

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

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

        new_name = path_basename(new_path);

        dir = get_parent_dentry(wim, new_path, WIMLIB_CASE_SENSITIVE);
        if (!dir)
                return -errno;

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

        if (get_dentry_child_with_name(dir, new_name, WIMLIB_CASE_SENSITIVE))
                return -EEXIST;

        if (new_dentry_with_existing_inode(new_name, inode, &new_alias))
                return -ENOMEM;

        dentry_add_child(dir, new_alias);
        touch_inode(dir->d_inode);
        return 0;
}

static int
wimfs_listxattr(const char *path, char *list, size_t size)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        const struct wim_inode *inode;
        char *p = list;
        int total_size = 0;

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

        /* List named data streams, or get the list size.  We report each named
         * data stream "X" as an extended attribute "user.X".  */

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

        for (unsigned i = 0; i < inode->i_num_streams; i++) {
                const struct wim_inode_stream *strm;
                char *stream_name_mbs;
                size_t stream_name_mbs_nbytes;

                strm = &inode->i_streams[i];

                if (!stream_is_named_data_stream(strm))
                        continue;

                if (utf16le_to_tstr(strm->stream_name,
                                    utf16le_len_bytes(strm->stream_name),
                                    &stream_name_mbs,
                                    &stream_name_mbs_nbytes))
                        return -errno;

                if (unlikely(INT_MAX - total_size < stream_name_mbs_nbytes + 6)) {
                        FREE(stream_name_mbs);
                        return -EFBIG;
                }

                total_size += stream_name_mbs_nbytes + 6;
                if (size) {
                        if (list + size - p < stream_name_mbs_nbytes + 6) {
                                FREE(stream_name_mbs);
                                return -ERANGE;
                        }
                        p = mempcpy(p, "user.", 5);
                        p = mempcpy(p, stream_name_mbs, stream_name_mbs_nbytes);
                        *p++ = '\0';
                }
                FREE(stream_name_mbs);
        }
        return total_size;
}

static int
wimfs_mkdir(const char *path, mode_t mode)
{
        struct wim_dentry *dentry;
        int ret;

        /* Note: according to fuse.h, mode may not include S_IFDIR  */
        ret = create_file(fuse_get_context(), path, mode | S_IFDIR, 0, &dentry);
        if (ret)
                return ret;
        touch_parent(dentry);
        return 0;
}

static int
wimfs_mknod(const char *path, mode_t mode, dev_t rdev)
{
        struct fuse_context *fuse_ctx = fuse_get_context();
        struct wimfs_context *wimfs_ctx = WIMFS_CTX(fuse_ctx);
        const char *stream_name;

        if ((wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS)
             && (stream_name = path_stream_name(path)))
        {
                struct wim_inode *inode;
                struct wim_inode_stream *existing_strm;
                struct wim_inode_stream *new_strm;
                char *p;
                const utf16lechar *uname;

                /* Create a named data stream.  */

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

                p = (char *)stream_name - 1;

                *p = '\0';
                inode = wim_pathname_to_inode(wimfs_ctx->wim, path);
                *p = ':';
                if (!inode)
                        return -errno;

                if (tstr_get_utf16le(stream_name, &uname))
                        return -errno;

                existing_strm = inode_get_stream(inode, STREAM_TYPE_DATA, uname);
                if (existing_strm) {
                        tstr_put_utf16le(uname);
                        return -EEXIST;
                }

                new_strm = inode_add_stream(inode, STREAM_TYPE_DATA, uname, NULL);

                tstr_put_utf16le(uname);

                if (!new_strm)
                        return -errno;
                return 0;
        } else {
                /* Create a regular file, device node, named pipe, or socket.
                 */
                struct wim_dentry *dentry;
                int ret;

                if (!S_ISREG(mode) &&
                    !(wimfs_ctx->mount_flags & WIMLIB_MOUNT_FLAG_UNIX_DATA))
                        return -EPERM;

                ret = create_file(fuse_ctx, path, mode, rdev, &dentry);
                if (ret)
                        return ret;
                touch_parent(dentry);
                return 0;
        }
}

static int
wimfs_open(const char *path, struct fuse_file_info *fi)
{
        struct wimfs_context *ctx = wimfs_get_context();
        struct wim_dentry *dentry;
        struct wim_inode *inode;
        struct wim_inode_stream *strm;
        struct blob_descriptor *blob;
        struct wimfs_fd *fd;
        int ret;

        ret = wim_pathname_to_stream(ctx, path, 0, &dentry, &strm);
        if (ret)
                return ret;

        inode = dentry->d_inode;
        blob = stream_blob_resolved(strm);

        /* The data of the file being opened 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 data directly
         * from the WIM file if we are opening it read-only, but we need to
         * extract the data to the staging directory if we are opening it
         * writable.  */

        if (flags_writable(fi->flags) &&
            (!blob || blob->blob_location != BLOB_IN_STAGING_FILE)) {
                ret = extract_blob_to_staging_dir(inode,
                                                  strm,
                                                  blob_size(blob),
                                                  ctx);
                if (ret)
                        return ret;
                blob = stream_blob_resolved(strm);
        }

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

        if (blob && blob->blob_location == BLOB_IN_STAGING_FILE) {
                int raw_fd;

                raw_fd = openat(blob->staging_dir_fd, blob->staging_file_name,
                                (fi->flags & (O_ACCMODE | O_TRUNC)) |
                                O_NOFOLLOW);
                if (raw_fd < 0) {
                        close_wimfs_fd(fd);
                        return -errno;
                }
                filedes_init(&fd->f_staging_fd, raw_fd);
                if (fi->flags & O_TRUNC) {
                        blob->size = 0;
                        file_contents_changed(inode);
                }
        }
        fi->fh = (uintptr_t)fd;
        return 0;
}

static int
wimfs_opendir(const char *path, struct fuse_file_info *fi)
{
        WIMStruct *wim = wimfs_get_WIMStruct();
        struct wim_inode *inode;
        struct wim_inode_stream *strm;
        struct wimfs_fd *fd;
        int ret;

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

static int
wimfs_read(const char *path, char *buf, size_t size,
           off_t offset, struct fuse_file_info *fi)
{
        struct wimfs_fd *fd = WIMFS_FD(fi);
        const struct blob_descriptor *blob;
        ssize_t ret;

        blob = fd->f_blob;
        if (!blob)
                return 0;

        if (offset >= blob->size)
                return 0;

        if (size > blob->size - offset)
                size = blob->size - offset;

        if (!size)
                return 0;

        switch (blob->blob_location) {
        case BLOB_IN_WIM:
                if (read_partial_wim_blob_into_buf(blob, offset, size, buf))
                        ret = errno ? -errno : -EIO;
                else
                        ret = size;
                break;
        case BLOB_IN_STAGING_FILE:
                ret = pread(fd->f_staging_fd.fd, buf, size, offset);
                if (ret < 0)
                        ret = -errno;
                break;
        case BLOB_IN_ATTACHED_BUFFER:
                memcpy(buf, blob->attached_buffer + offset, size);
                ret = size;
                break;
        default:
                ret = -EINVAL;
                break;
        }
        return ret;
}

static int
wimfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
              off_t offset, struct fuse_file_info *fi,
              enum fuse_readdir_flags flags)
{
        struct wimfs_fd *fd = WIMFS_FD(fi);
        const struct wim_inode *inode;
        const struct wim_dentry *child;
        int ret;

        inode = fd->f_inode;

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

        for_inode_child(child, inode) {
                char *name;
                size_t name_nbytes;

                if (utf16le_to_tstr(child->d_name, child->d_name_nbytes,
                                    &name, &name_nbytes))
                        return -errno;

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

static int
wimfs_readlink(const char *path, char *buf, size_t bufsize)
{
        struct wimfs_context *ctx = wimfs_get_context();
        const struct wim_inode *inode;
        int ret;

        inode = wim_pathname_to_inode(ctx->wim, path);
        if (!inode)
                return -errno;
        if (bufsize <= 0)
                return -EINVAL;
        ret = wim_inode_readlink(inode, buf, bufsize - 1, NULL,
                                 ctx->mountpoint_abspath,
                                 ctx->mountpoint_abspath_nchars);
        if (ret < 0)
                return ret;
        buf[ret] = '\0';
        return 0;
}

/* We use this for both release() and releasedir(), since in both cases we
 * simply need to close the file descriptor.  */
static int
wimfs_release(const char *path, struct fuse_file_info *fi)
{
        return close_wimfs_fd(WIMFS_FD(fi));
}

static int
wimfs_removexattr(const char *path, const char *name)
{
        struct wimfs_context *ctx = wimfs_get_context();
        struct wim_inode *inode;
        struct wim_inode_stream *strm;

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

        if (strncmp(name, "user.", 5))
                return -ENOATTR;
        name += 5;

        if (!*name)
                return -ENOATTR;

        /* Removing a named data stream.  */

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

        strm = inode_get_data_stream_tstr(inode, name);
        if (!strm)
                return (errno == ENOENT) ? -ENOATTR : -errno;

        inode_remove_stream(inode, strm, ctx->wim->blob_table);
        return 0;
}

static int
wimfs_rename(const char *from, const char *to, unsigned int flags)
{
        if (flags & RENAME_EXCHANGE)
                return -EINVAL;
        return rename_wim_path(wimfs_get_WIMStruct(), from, to,
                               WIMLIB_CASE_SENSITIVE,
                               (flags & RENAME_NOREPLACE), NULL);
}

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

        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;

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

static int
wimfs_setxattr(const char *path, const char *name,
               const char *value, size_t size, int flags)
{
        struct wimfs_context *ctx = wimfs_get_context();
        struct wim_inode *inode;
        struct wim_inode_stream *strm;
        const utf16lechar *uname;
        int ret;

        if (!strncmp(name, "wimfs.", 6)) {
                /* Handle some magical extended attributes.  These really should
                 * be ioctls, but directory ioctls aren't supported until
                 * libfuse 2.9, and even then they are broken.  [Fixed by
                 * libfuse commit e3b7d4c278a26520be63d99d6ea84b26906fe73d]  */
                name += 6;
                if (!strcmp(name, "unmount_info")) {
                        if (!may_unmount_wimfs())
                                return -EPERM;
                        if (size < sizeof(struct wimfs_unmount_info))
                                return -EINVAL;
                        memcpy(&ctx->unmount_info, value,
                               sizeof(struct wimfs_unmount_info));
                        return 0;
                }
                return -ENOATTR;
        }

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

        if (strncmp(name, "user.", 5))
                return -ENOATTR;
        name += 5;

        if (!*name)
                return -ENOATTR;

        /* Setting the contents of a named data stream.  */

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

        ret = tstr_get_utf16le(name, &uname);
        if (ret)
                return -errno;

        strm = inode_get_stream(inode, STREAM_TYPE_DATA, uname);
        if (strm) {
                ret = -EEXIST;
                if (flags & XATTR_CREATE)
                        goto out_put_uname;
        } else {
                ret = -ENOATTR;
                if (flags & XATTR_REPLACE)
                        goto out_put_uname;
        }

        if (strm) {
                if (!inode_replace_stream_data(inode, strm, value, size,
                                               ctx->wim->blob_table))
                {
                        ret = -errno;
                        goto out_put_uname;
                }
        } else {
                if (!inode_add_stream_with_data(inode, STREAM_TYPE_DATA, uname,
                                                value, size, ctx->wim->blob_table))
                {
                        ret = -errno;
                        goto out_put_uname;
                }
        }

        ret = 0;
out_put_uname:
        tstr_put_utf16le(uname);
        return ret;
}

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_file(fuse_ctx, from, S_IFLNK | 0777, 0, &dentry);
        if (ret)
                return ret;
        ret = wim_inode_set_symlink(dentry->d_inode, to,
                                    wimfs_ctx->wim->blob_table);
        if (ret) {
                remove_dentry(dentry, wimfs_ctx->wim->blob_table);
                if (ret == WIMLIB_ERR_NOMEM)
                        ret = -ENOMEM;
                else
                        ret = -EINVAL;
        } else {
                touch_parent(dentry);
        }
        return ret;
}

static int
do_truncate(int staging_fd, off_t size,
            struct wim_inode *inode, struct blob_descriptor *blob)
{
        if (ftruncate(staging_fd, size))
                return -errno;
        file_contents_changed(inode);
        blob->size = size;
        return 0;
}

static int
wimfs_truncate(const char *path, off_t size, struct fuse_file_info *fi)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        struct wim_dentry *dentry;
        struct wim_inode_stream *strm;
        struct blob_descriptor *blob;
        int ret;
        int staging_fd;

        if (fi) {
                struct wimfs_fd *fd = WIMFS_FD(fi);

                return do_truncate(fd->f_staging_fd.fd, size, fd->f_inode,
                                   fd->f_blob);
        }

        ret = wim_pathname_to_stream(ctx, path, 0, &dentry, &strm);
        if (ret)
                return ret;

        blob = stream_blob_resolved(strm);

        if (!blob && !size)
                return 0;

        if (!blob || blob->blob_location != BLOB_IN_STAGING_FILE) {
                return extract_blob_to_staging_dir(dentry->d_inode,
                                                   strm, size, ctx);
        }

        /* Truncate the staging file.  */
        staging_fd = openat(blob->staging_dir_fd, blob->staging_file_name,
                            O_WRONLY | O_NOFOLLOW);
        if (staging_fd < 0)
                return -errno;
        ret = do_truncate(staging_fd, size, dentry->d_inode, blob);
        if (close(staging_fd) && !ret)
                ret = -errno;
        return ret;
}

static int
wimfs_unlink(const char *path)
{
        const struct wimfs_context *ctx = wimfs_get_context();
        struct wim_dentry *dentry;
        struct wim_inode_stream *strm;
        int ret;

        ret = wim_pathname_to_stream(ctx, path, 0, &dentry, &strm);
        if (ret)
                return ret;

        if (stream_is_named(strm)) {
                inode_remove_stream(dentry->d_inode, strm,
                                    ctx->wim->blob_table);
        } else {
                touch_parent(dentry);
                remove_dentry(dentry, ctx->wim->blob_table);
        }
        return 0;
}

/*
 * 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 fuse_file_info *fi)
{
        struct wim_inode *inode;

        if (fi) {
                inode = WIMFS_FD(fi)->f_inode;
        } else {
                inode = wim_pathname_to_inode(wimfs_get_WIMStruct(), path);
                if (!inode)
                        return -errno;
        }

        if (tv[0].tv_nsec != UTIME_OMIT) {
                if (tv[0].tv_nsec == UTIME_NOW)
                        inode->i_last_access_time = now_as_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 = now_as_wim_timestamp();
                else
                        inode->i_last_write_time = timespec_to_wim_timestamp(&tv[1]);
        }
        return 0;
}

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 = WIMFS_FD(fi);
        ssize_t ret;

        ret = pwrite(fd->f_staging_fd.fd, buf, size, offset);
        if (ret < 0)
                return -errno;

        if (offset + size > fd->f_blob->size)
                fd->f_blob->size = offset + size;

        file_contents_changed(fd->f_inode);
        return ret;
}

static const struct fuse_operations wimfs_operations = {
        .init        = wimfs_init,
        .chmod       = wimfs_chmod,
        .chown       = wimfs_chown,
        .getattr     = wimfs_getattr,
        .getxattr    = wimfs_getxattr,
        .link        = wimfs_link,
        .listxattr   = wimfs_listxattr,
        .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_release,
        .removexattr = wimfs_removexattr,
        .rename      = wimfs_rename,
        .rmdir       = wimfs_rmdir,
        .setxattr    = wimfs_setxattr,
        .symlink     = wimfs_symlink,
        .truncate    = wimfs_truncate,
        .unlink      = wimfs_unlink,
        .utimens     = wimfs_utimens,
        .write       = wimfs_write,

};

/* 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 ret;
        struct wim_image_metadata *imd;
        struct wimfs_context ctx;
        char *fuse_argv[16];
        int fuse_argc;

        if (!wim || !dir || !*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;

        /* For read-write mount, check for write access to the WIM.  */
        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                if (!wim->filename)
                        return WIMLIB_ERR_NO_FILENAME;
                ret = can_modify_wim(wim);
                if (ret)
                        return ret;
        }

        /* Select the image to mount.  */
        ret = select_wim_image(wim, image);
        if (ret)
                return ret;

        /* Get the metadata for the image to mount.  */
        imd = wim_get_current_image_metadata(wim);

        /* To avoid complicating things, we don't support mounting images to
         * which in-memory modifications have already been made.  */
        if (is_image_dirty(imd)) {
                ERROR("Cannot mount a modified WIM image!");
                return WIMLIB_ERR_INVALID_PARAM;
        }

        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                if (imd->refcnt > 1)
                        return WIMLIB_ERR_IMAGE_HAS_MULTIPLE_REFERENCES;
                ret = lock_wim_for_append(wim);
                if (ret)
                        return ret;
        }

        if (wim_has_solid_resources(wim)) {
                WARNING("Mounting a WIM file containing solid-compressed data; "
                        "file access may be slow.");
        }

        /* If the user did not specify an interface for accessing named
         * data streams, use the default (extended attributes).  */
        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;

        /* Start initializing the wimfs_context.  */
        memset(&ctx, 0, sizeof(struct wimfs_context));
        ctx.wim = wim;
        ctx.mount_flags = mount_flags;
        if (mount_flags & WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS)
                ctx.default_lookup_flags = LOOKUP_FLAG_ADS_OK;

        /* For read-write mounts, create the staging directory, save a reference
         * to the image's metadata resource, and mark the image dirty.  */
        if (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE) {
                ret = make_staging_dir(&ctx, staging_dir);
                if (ret)
                        goto out;
                ret = WIMLIB_ERR_NOMEM;
                ctx.metadata_resource = clone_blob_descriptor(
                                                        imd->metadata_blob);
                if (!ctx.metadata_resource)
                        goto out;
                mark_image_dirty(imd);
        }
        ctx.owner_uid = getuid();
        ctx.owner_gid = getgid();

        /* Number the inodes in the mounted image sequentially and initialize
         * the file descriptor arrays  */
        prepare_inodes(&ctx);

        /* Save the absolute path to the mountpoint directory.  */
        ctx.mountpoint_abspath = realpath(dir, NULL);
        if (ctx.mountpoint_abspath)
                ctx.mountpoint_abspath_nchars = strlen(ctx.mountpoint_abspath);

        /* Build the FUSE command line.  */

        fuse_argc = 0;
        fuse_argv[fuse_argc++] = "wimlib";
        fuse_argv[fuse_argc++] = (char *)dir;

        /* Disable multi-threaded operation.  */
        fuse_argv[fuse_argc++] = "-s";

        /* Enable FUSE debug mode (don't fork) if requested by the user.  */
        if (mount_flags & WIMLIB_MOUNT_FLAG_DEBUG)
                fuse_argv[fuse_argc++] = "-d";

        /*
         * Build the FUSE mount options:
         *
         * subtype=wimfs
         *      Name for our filesystem (main type is "fuse").
         *
         * default_permissions
         *      FUSE will perform permission checking.  Useful when
         *      WIMLIB_MOUNT_FLAG_UNIX_DATA is provided and the WIM image
         *      contains the UNIX permissions for each file.
         */
        char optstring[128] = "subtype=wimfs,default_permissions";
        fuse_argv[fuse_argc++] = "-o";
        fuse_argv[fuse_argc++] = optstring;
        if (!(mount_flags & WIMLIB_MOUNT_FLAG_READWRITE))
                strcat(optstring, ",ro");
        if (mount_flags & WIMLIB_MOUNT_FLAG_ALLOW_OTHER)
                strcat(optstring, ",allow_other");
        fuse_argv[fuse_argc] = NULL;

        /* Mount our filesystem.  */
        ret = fuse_main(fuse_argc, fuse_argv, &wimfs_operations, &ctx);

        /* Cleanup and return.  */
        if (ret)
                ret = WIMLIB_ERR_FUSE;
out:
        FREE(ctx.mountpoint_abspath);
        free_blob_descriptor(ctx.metadata_resource);
        if (ctx.staging_dir_name)
                delete_staging_dir(&ctx);
        unlock_wim_for_append(wim);
        return ret;
}

struct commit_progress_thread_args {
        mqd_t mq;
        wimlib_progress_func_t progfunc;
        void *progctx;
};

static void *
commit_progress_thread_proc(void *_args)
{
        struct commit_progress_thread_args *args = _args;
        struct commit_progress_report report;
        ssize_t ret;

        for (;;) {
                ret = mq_receive(args->mq,
                                 (char *)&report, sizeof(report), NULL);
                if (ret == sizeof(report)) {
                        call_progress(args->progfunc, report.msg,
                                      &report.info, args->progctx);
                } else {
                        if (ret == 0 || (ret < 0 && errno != EINTR))
                                break;
                }
        }
        return NULL;
}

static void
generate_message_queue_name(char name[WIMFS_MQUEUE_NAME_LEN + 1])
{
        name[0] = '/';
        memcpy(name + 1, "wimfs-", 6);
        get_random_alnum_chars(name + 7, WIMFS_MQUEUE_NAME_LEN - 7);
        name[WIMFS_MQUEUE_NAME_LEN] = '\0';
}

static mqd_t
create_message_queue(const char *name)
{
        bool am_root;
        mode_t umask_save;
        mode_t mode;
        struct mq_attr attr;
        mqd_t mq;

        memset(&attr, 0, sizeof(attr));
        attr.mq_maxmsg = 8;
        attr.mq_msgsize = sizeof(struct commit_progress_report);

        am_root = (geteuid() == 0);
        if (am_root) {
                /* Filesystem mounted as normal user with --allow-other should
                 * be able to send messages to root user, if they're doing the
                 * unmount.  */
                umask_save = umask(0);
                mode = 0666;
        } else {
                mode = 0600;
        }
        mq = mq_open(name, O_RDWR | O_CREAT | O_EXCL, mode, &attr);
        if (am_root)
                umask(umask_save);
        return mq;
}

/* Unmount a read-only or read-write mounted WIM image.  */
static int
do_unmount(const char *dir)
{
        int status;
        ssize_t len;

        len = getxattr(dir, "wimfs.unmount", &status, sizeof(int));
        if (len == sizeof(int))
                return status;
        else if (len < 0 && (errno == EACCES || errno == EPERM))
                return WIMLIB_ERR_NOT_PERMITTED_TO_UNMOUNT;
        else
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;
}

static int
set_unmount_info(const char *dir, const struct wimfs_unmount_info *unmount_info)
{
        if (!setxattr(dir, "wimfs.unmount_info",
                      unmount_info, sizeof(struct wimfs_unmount_info), 0))
                return 0;
        else if (errno == EROFS)
                return 0;
        else if (errno == EACCES || errno == EPERM)
                return WIMLIB_ERR_NOT_PERMITTED_TO_UNMOUNT;
        else
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;
}

static int
do_unmount_discard(const char *dir)
{
        int ret;
        struct wimfs_unmount_info unmount_info;

        memset(&unmount_info, 0, sizeof(unmount_info));

        ret = set_unmount_info(dir, &unmount_info);
        if (ret)
                return ret;
        return do_unmount(dir);
}

/* Unmount a read-write mounted WIM image, committing the changes.  */
static int
do_unmount_commit(const char *dir, int unmount_flags,
                  wimlib_progress_func_t progfunc, void *progctx)
{
        struct wimfs_unmount_info unmount_info;
        mqd_t mq = (mqd_t)-1;
        struct commit_progress_thread_args args;
        struct thread commit_progress_tid;
        int ret;

        memset(&unmount_info, 0, sizeof(unmount_info));
        unmount_info.unmount_flags = unmount_flags;

        /* The current thread will be stuck in getxattr() until the image is
         * committed.  Create a thread to handle the progress messages.  */
        if (progfunc) {
                generate_message_queue_name(unmount_info.mq_name);

                mq = create_message_queue(unmount_info.mq_name);
                if (mq == (mqd_t)-1) {
                        ERROR_WITH_ERRNO("Can't create POSIX message queue");
                        return WIMLIB_ERR_MQUEUE;
                }
                args.mq = mq;
                args.progfunc = progfunc;
                args.progctx = progctx;
                if (!thread_create(&commit_progress_tid,
                                   commit_progress_thread_proc, &args)) {
                        ret = WIMLIB_ERR_NOMEM;
                        goto out_delete_mq;
                }
                unmount_info.unmount_flags |= WIMLIB_UNMOUNT_FLAG_SEND_PROGRESS;
        }

        ret = set_unmount_info(dir, &unmount_info);
        if (!ret)
                ret = do_unmount(dir);
        if (progfunc) {
                /* Terminate the progress thread.  */
                char empty[1];
                mq_send(mq, empty, 0, 1);
                thread_join(&commit_progress_tid);
        }
out_delete_mq:
        if (progfunc) {
                mq_close(mq);
                mq_unlink(unmount_info.mq_name);
        }
        return ret;
}

static int
begin_unmount(const char *dir, int unmount_flags, int *mount_flags_ret,
              wimlib_progress_func_t progfunc, void *progctx)
{
        int mount_flags;
        int mounted_image;
        int wim_filename_len;
        union wimlib_progress_info progress;

        if (getxattr(dir, "wimfs.mount_flags",
                     &mount_flags, sizeof(int)) != sizeof(int))
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;

        *mount_flags_ret = mount_flags;

        if (!progfunc)
                return 0;

        if (getxattr(dir, "wimfs.mounted_image",
                     &mounted_image, sizeof(int)) != sizeof(int))
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;

        wim_filename_len = getxattr(dir, "wimfs.wim_filename", NULL, 0);
        if (wim_filename_len < 0)
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;

        char wim_filename[wim_filename_len + 1];
        if (getxattr(dir, "wimfs.wim_filename",
                     wim_filename, wim_filename_len) != wim_filename_len)
                return WIMLIB_ERR_NOT_A_MOUNTPOINT;
        wim_filename[wim_filename_len] = '\0';

        progress.unmount.mountpoint = dir;
        progress.unmount.mounted_wim = wim_filename;
        progress.unmount.mounted_image = mounted_image;
        progress.unmount.mount_flags = mount_flags;
        progress.unmount.unmount_flags = unmount_flags;

        return call_progress(progfunc, WIMLIB_PROGRESS_MSG_UNMOUNT_BEGIN,
                             &progress, progctx);
}

/* API function documented in wimlib.h  */
WIMLIBAPI int
wimlib_unmount_image_with_progress(const char *dir, int unmount_flags,
                                   wimlib_progress_func_t progfunc, void *progctx)
{
        int mount_flags;
        int ret;

        ret = wimlib_global_init(0);
        if (ret)
                return ret;

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

        ret = begin_unmount(dir, unmount_flags, &mount_flags,
                            progfunc, progctx);
        if (ret)
                return ret;

        if ((unmount_flags & WIMLIB_UNMOUNT_FLAG_COMMIT) &&
            (mount_flags & WIMLIB_MOUNT_FLAG_READWRITE))
                return do_unmount_commit(dir, unmount_flags,
                                         progfunc, progctx);
        else
                return do_unmount_discard(dir);
}

#else /* WITH_FUSE */


static int
mount_unsupported_error(void)
{
#ifdef _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_with_progress(const tchar *dir, int unmount_flags,
                                   wimlib_progress_func_t progfunc, void *progctx)
{
        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 */

WIMLIBAPI int
wimlib_unmount_image(const tchar *dir, int unmount_flags)
{
        return wimlib_unmount_image_with_progress(dir, unmount_flags, NULL, NULL);
}