/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2007-2009 Google Inc. and Amit Singh
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following disclaimer
 *   in the documentation and/or other materials provided with the
 *   distribution.
 * * Neither the name of Google Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright (C) 2005 Csaba Henk.
 * All rights reserved.
 *
 * Copyright (c) 2019 The FreeBSD Foundation
 *
 * Portions of this software were developed by BFF Storage Systems, LLC under
 * sponsorship from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/buf.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/capsicum.h>
#include <sys/conf.h>
#include <sys/filedesc.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/fcntl.h>
#define EXTERR_CATEGORY EXTERR_CAT_FUSE_VFS
#include <sys/exterrvar.h>

#include "fuse.h"
#include "fuse_node.h"
#include "fuse_ipc.h"
#include "fuse_internal.h"

#include <sys/priv.h>
#include <security/mac/mac_framework.h>

SDT_PROVIDER_DECLARE(fusefs);
/* 
 * Fuse trace probe:
 * arg0: verbosity.  Higher numbers give more verbose messages
 * arg1: Textual message
 */
SDT_PROBE_DEFINE2(fusefs, , vfsops, trace, "int", "char*");

/* This will do for privilege types for now */
#ifndef PRIV_VFS_FUSE_ALLOWOTHER
#define PRIV_VFS_FUSE_ALLOWOTHER PRIV_VFS_MOUNT_NONUSER
#endif
#ifndef PRIV_VFS_FUSE_MOUNT_NONUSER
#define PRIV_VFS_FUSE_MOUNT_NONUSER PRIV_VFS_MOUNT_NONUSER
#endif
#ifndef PRIV_VFS_FUSE_SYNC_UNMOUNT
#define PRIV_VFS_FUSE_SYNC_UNMOUNT PRIV_VFS_MOUNT_NONUSER
#endif

static vfs_fhtovp_t fuse_vfsop_fhtovp;
static vfs_mount_t fuse_vfsop_mount;
static vfs_unmount_t fuse_vfsop_unmount;
static vfs_root_t fuse_vfsop_root;
static vfs_statfs_t fuse_vfsop_statfs;
static vfs_vget_t fuse_vfsop_vget;

struct vfsops fuse_vfsops = {
        .vfs_fhtovp = fuse_vfsop_fhtovp,
        .vfs_mount = fuse_vfsop_mount,
        .vfs_unmount = fuse_vfsop_unmount,
        .vfs_root = fuse_vfsop_root,
        .vfs_statfs = fuse_vfsop_statfs,
        .vfs_vget = fuse_vfsop_vget,
};

static int fuse_enforce_dev_perms = 0;

SYSCTL_INT(_vfs_fusefs, OID_AUTO, enforce_dev_perms, CTLFLAG_RW,
    &fuse_enforce_dev_perms, 0,
    "enforce fuse device permissions for secondary mounts");

MALLOC_DEFINE(M_FUSEVFS, "fuse_filesystem", "buffer for fuse vfs layer");

static int
fuse_getdevice(const char *fspec, struct thread *td, struct cdev **fdevp)
{
        struct nameidata nd, *ndp = &nd;
        struct vnode *devvp;
        struct cdev *fdev;
        int err;

        /*
         * Not an update, or updating the name: look up the name
         * and verify that it refers to a sensible disk device.
         */

        NDINIT(ndp, LOOKUP, FOLLOW, UIO_SYSSPACE, fspec);
        if ((err = namei(ndp)) != 0)
                return err;
        NDFREE_PNBUF(ndp);
        devvp = ndp->ni_vp;

        if (devvp->v_type != VCHR) {
                vrele(devvp);
                return ENXIO;
        }
        fdev = devvp->v_rdev;
        dev_ref(fdev);

        if (fuse_enforce_dev_perms) {
                /*
                 * Check if mounter can open the fuse device.
                 *
                 * This has significance only if we are doing a secondary mount
                 * which doesn't involve actually opening fuse devices, but we
                 * still want to enforce the permissions of the device (in
                 * order to keep control over the circle of fuse users).
                 *
                 * (In case of primary mounts, we are either the superuser so
                 * we can do anything anyway, or we can mount only if the
                 * device is already opened by us, ie. we are permitted to open
                 * the device.)
                 */
#if 0
#ifdef MAC
                err = mac_check_vnode_open(td->td_ucred, devvp, VREAD | VWRITE);
                if (!err)
#endif
#endif /* 0 */
                        err = VOP_ACCESS(devvp, VREAD | VWRITE, td->td_ucred, td);
                if (err) {
                        vrele(devvp);
                        dev_rel(fdev);
                        return err;
                }
        }
        /*
         * according to coda code, no extra lock is needed --
         * although in sys/vnode.h this field is marked "v"
         */
        vrele(devvp);

        if (!fdev->si_devsw ||
            strcmp("fuse", fdev->si_devsw->d_name)) {
                dev_rel(fdev);
                return ENXIO;
        }
        *fdevp = fdev;

        return 0;
}

#define FUSE_FLAGOPT(fnam, fval) do {                           \
        vfs_flagopt(opts, #fnam, &mntopts, fval);               \
        vfs_flagopt(opts, "__" #fnam, &__mntopts, fval);        \
} while (0)

SDT_PROBE_DEFINE1(fusefs, , vfsops, mntopts, "uint64_t");
SDT_PROBE_DEFINE4(fusefs, , vfsops, mount_err, "char*", "struct fuse_data*",
        "struct mount*", "int");

static int
fuse_vfs_remount(struct mount *mp, struct thread *td, uint64_t mntopts,
        uint32_t max_read, int daemon_timeout)
{
        int err = 0;
        struct fuse_data *data = fuse_get_mpdata(mp);
        /* Don't allow these options to be changed */
        const static unsigned long long cant_update_opts = 
                MNT_USER;       /* Mount owner must be the user running the daemon */

        FUSE_LOCK();

        if ((mp->mnt_flag ^ data->mnt_flag) & cant_update_opts) {
                err = EOPNOTSUPP;
                SDT_PROBE4(fusefs, , vfsops, mount_err,
                        "Can't change these mount options during remount",
                        data, mp, err);
                goto out;
        }
        if (((data->dataflags ^ mntopts) & FSESS_MNTOPTS_MASK) ||
             (data->max_read != max_read) ||
             (data->daemon_timeout != daemon_timeout)) {
                // TODO: allow changing options where it makes sense
                err = EOPNOTSUPP;
                SDT_PROBE4(fusefs, , vfsops, mount_err,
                        "Can't change fuse mount options during remount",
                        data, mp, err);
                goto out;
        }

        if (fdata_get_dead(data)) {
                err = ENOTCONN;
                SDT_PROBE4(fusefs, , vfsops, mount_err,
                        "device is dead during mount", data, mp, err);
                goto out;
        }

        /* Sanity + permission checks */
        if (!data->daemoncred)
                panic("fuse daemon found, but identity unknown");
        if (mntopts & FSESS_DAEMON_CAN_SPY)
                err = priv_check(td, PRIV_VFS_FUSE_ALLOWOTHER);
        if (err == 0 && td->td_ucred->cr_uid != data->daemoncred->cr_uid)
                /* are we allowed to do the first mount? */
                err = priv_check(td, PRIV_VFS_FUSE_MOUNT_NONUSER);

out:
        FUSE_UNLOCK();
        return err;
}

static int
fuse_vfsop_fhtovp(struct mount *mp, struct fid *fhp, int flags,
        struct vnode **vpp)
{
        struct fuse_fid *ffhp = (struct fuse_fid *)fhp;
        struct fuse_vnode_data *fvdat;
        struct vnode *nvp;
        int error;

        if (!(fuse_get_mpdata(mp)->dataflags & FSESS_EXPORT_SUPPORT))
                return (EXTERROR(EOPNOTSUPP, "NFS-style lookups are not supported"));

        error = VFS_VGET(mp, ffhp->nid, LK_EXCLUSIVE, &nvp);
        if (error) {
                *vpp = NULL;
                return (error);
        }
        fvdat = VTOFUD(nvp);
        if (fvdat->generation != ffhp->gen ) {
                vput(nvp);
                *vpp = NULL;
                return (ESTALE);
        }
        *vpp = nvp;
        vnode_create_vobject(*vpp, VNODE_NO_SIZE, curthread);
        return (0);
}

static int
fuse_vfsop_mount(struct mount *mp)
{
        int err;

        uint64_t mntopts, __mntopts;
        uint32_t max_read;
        int linux_errnos;
        int daemon_timeout;
        int fd;

        struct cdev *fdev;
        struct fuse_data *data = NULL;
        struct thread *td;
        struct file *fp, *fptmp;
        char *fspec, *subtype, *fsname = NULL;
        int fsnamelen;
        struct vfsoptlist *opts;

        subtype = NULL;
        max_read = ~0;
        linux_errnos = 0;
        err = 0;
        mntopts = 0;
        __mntopts = 0;
        td = curthread;

        /* Get the new options passed to mount */
        opts = mp->mnt_optnew;

        if (!opts)
                return (EXTERROR(EINVAL, "Mount options were not supplied"));

        /* `fspath' contains the mount point (eg. /mnt/fuse/sshfs); REQUIRED */
        if (!vfs_getopts(opts, "fspath", &err))
                return (EXTERROR(err, "Mount options are missing 'fspath'"));

        /*
         * With the help of underscored options the mount program
         * can inform us from the flags it sets by default
         */
        FUSE_FLAGOPT(allow_other, FSESS_DAEMON_CAN_SPY);
        FUSE_FLAGOPT(push_symlinks_in, FSESS_PUSH_SYMLINKS_IN);
        FUSE_FLAGOPT(default_permissions, FSESS_DEFAULT_PERMISSIONS);
        FUSE_FLAGOPT(intr, FSESS_INTR);
        FUSE_FLAGOPT(auto_unmount, FSESS_AUTO_UNMOUNT);

        (void)vfs_scanopt(opts, "max_read=", "%u", &max_read);
        (void)vfs_scanopt(opts, "linux_errnos", "%d", &linux_errnos);
        if (vfs_scanopt(opts, "timeout=", "%u", &daemon_timeout) == 1) {
                if (daemon_timeout < FUSE_MIN_DAEMON_TIMEOUT)
                        daemon_timeout = FUSE_MIN_DAEMON_TIMEOUT;
                else if (daemon_timeout > FUSE_MAX_DAEMON_TIMEOUT)
                        daemon_timeout = FUSE_MAX_DAEMON_TIMEOUT;
        } else {
                daemon_timeout = FUSE_DEFAULT_DAEMON_TIMEOUT;
        }
        subtype = vfs_getopts(opts, "subtype=", &err);

        SDT_PROBE1(fusefs, , vfsops, mntopts, mntopts);

        if (mp->mnt_flag & MNT_UPDATE) {
                return fuse_vfs_remount(mp, td, mntopts, max_read,
                        daemon_timeout);
        }

        /* `from' contains the device name (eg. /dev/fuse0); REQUIRED */
        fspec = vfs_getopts(opts, "from", &err);
        if (!fspec)
                return (EXTERROR(err, "Mount options are missing 'from'"));

        /* `fd' contains the filedescriptor for this session; REQUIRED */
        if (vfs_scanopt(opts, "fd", "%d", &fd) != 1)
                return (EXTERROR(EINVAL, "Mount options contain an invalid value "
                    "for 'fd'"));

        err = fuse_getdevice(fspec, td, &fdev);
        if (err != 0)
                return err;

        err = fget(td, fd, &cap_read_rights, &fp);
        if (err != 0) {
                SDT_PROBE2(fusefs, , vfsops, trace, 1,
                        "invalid or not opened device");
                goto out;
        }
        fptmp = td->td_fpop;
        td->td_fpop = fp;
        err = devfs_get_cdevpriv((void **)&data);
        td->td_fpop = fptmp;
        fdrop(fp, td);
        FUSE_LOCK();

        if (err != 0 || data == NULL) {
                err = ENXIO;
                SDT_PROBE4(fusefs, , vfsops, mount_err,
                        "invalid or not opened device", data, mp, err);
                FUSE_UNLOCK();
                goto out;
        }
        if (fdata_get_dead(data)) {
                err = ENOTCONN;
                SDT_PROBE4(fusefs, , vfsops, mount_err,
                        "device is dead during mount", data, mp, err);
                FUSE_UNLOCK();
                goto out;
        }
        /* Sanity + permission checks */
        if (!data->daemoncred)
                panic("fuse daemon found, but identity unknown");
        if (mntopts & FSESS_DAEMON_CAN_SPY) {
                err = priv_check(td, PRIV_VFS_FUSE_ALLOWOTHER);
                EXTERROR(err, "FUSE daemon requires privileges "
                    "due to 'allow_other' option");
        }
        if (err == 0 && td->td_ucred->cr_uid != data->daemoncred->cr_uid) {
                /* are we allowed to do the first mount? */
                err = priv_check(td, PRIV_VFS_FUSE_MOUNT_NONUSER);
                EXTERROR(err, "Mounting as a user that is different from the FUSE "
                    "daemon's requires privileges");
        }
        if (err) {
                FUSE_UNLOCK();
                goto out;
        }
        data->ref++;
        data->mp = mp;
        data->dataflags |= mntopts;
        data->max_read = max_read;
        data->daemon_timeout = daemon_timeout;
        data->linux_errnos = linux_errnos;
        data->mnt_flag = mp->mnt_flag & MNT_UPDATEMASK;
        FUSE_UNLOCK();

        vfs_getnewfsid(mp);
        MNT_ILOCK(mp);
        mp->mnt_data = data;
        /* 
         * FUSE file systems can be either local or remote, but the kernel
         * can't tell the difference.
         */
        mp->mnt_flag &= ~MNT_LOCAL;
        mp->mnt_kern_flag |= MNTK_USES_BCACHE;
        /* 
         * Disable nullfs cacheing because it can consume too many resources in
         * the FUSE server.
         */
        mp->mnt_kern_flag |= MNTK_NULL_NOCACHE;
        MNT_IUNLOCK(mp);
        /* We need this here as this slot is used by getnewvnode() */
        mp->mnt_stat.f_iosize = maxbcachebuf;
        if (subtype) {
                strlcat(mp->mnt_stat.f_fstypename, ".", MFSNAMELEN);
                strlcat(mp->mnt_stat.f_fstypename, subtype, MFSNAMELEN);
        }
        memset(mp->mnt_stat.f_mntfromname, 0, MNAMELEN);
        vfs_getopt(opts, "fsname=", (void**)&fsname, &fsnamelen);
        strlcpy(mp->mnt_stat.f_mntfromname,
                fsname == NULL ? fspec : fsname, MNAMELEN);
        mp->mnt_iosize_max = maxphys;

        /* Now handshaking with daemon */
        fuse_internal_send_init(data, td);

out:
        if (err) {
                FUSE_LOCK();
                if (data != NULL && data->mp == mp) {
                        /*
                         * Destroy device only if we acquired reference to
                         * it
                         */
                        SDT_PROBE4(fusefs, , vfsops, mount_err,
                                "mount failed, destroy device", data, mp, err);
                        data->mp = NULL;
                        mp->mnt_data = NULL;
                        fdata_trydestroy(data);
                }
                FUSE_UNLOCK();
                dev_rel(fdev);
        }
        return err;
}

static int
fuse_vfsop_unmount(struct mount *mp, int mntflags)
{
        int err = 0;
        int flags = 0;

        struct cdev *fdev;
        struct fuse_data *data;
        struct fuse_dispatcher fdi;
        struct thread *td = curthread;

        if (mntflags & MNT_FORCE) {
                flags |= FORCECLOSE;
        }
        data = fuse_get_mpdata(mp);
        if (!data) {
                panic("no private data for mount point?");
        }
        /* There is 1 extra root vnode reference (mp->mnt_data). */
        FUSE_LOCK();
        if (data->vroot != NULL) {
                struct vnode *vroot = data->vroot;

                data->vroot = NULL;
                FUSE_UNLOCK();
                vrele(vroot);
        } else
                FUSE_UNLOCK();
        err = vflush(mp, 0, flags, td);
        if (err) {
                return err;
        }
        if (fdata_get_dead(data)) {
                goto alreadydead;
        }
        if (fsess_maybe_impl(mp, FUSE_DESTROY)) {
                fdisp_init(&fdi, 0);
                fdisp_make(&fdi, FUSE_DESTROY, mp, 0, td, NULL);

                (void)fdisp_wait_answ(&fdi);
                fdisp_destroy(&fdi);
        }

        fdata_set_dead(data);

alreadydead:
        FUSE_LOCK();
        data->mp = NULL;
        fdev = data->fdev;
        fdata_trydestroy(data);
        FUSE_UNLOCK();

        MNT_ILOCK(mp);
        mp->mnt_data = NULL;
        MNT_IUNLOCK(mp);

        dev_rel(fdev);

        return 0;
}

SDT_PROBE_DEFINE1(fusefs, , vfsops, invalidate_without_export,
        "struct mount*");
static int
fuse_vfsop_vget(struct mount *mp, ino_t ino, int flags, struct vnode **vpp)
{
        struct fuse_data *data = fuse_get_mpdata(mp);
        uint64_t nodeid = ino;
        struct thread *td = curthread;
        struct fuse_dispatcher fdi;
        struct fuse_entry_out *feo;
        struct fuse_vnode_data *fvdat;
        struct timespec now;
        const char dot[] = ".";
        __enum_uint8(vtype) vtyp;
        int error;

        if (!(data->dataflags & FSESS_EXPORT_SUPPORT)) {
                /*
                 * Unreachable unless you do something stupid, like export a
                 * nullfs mount of a fusefs file system.
                 */
                SDT_PROBE1(fusefs, , vfsops, invalidate_without_export, mp);
                return (EXTERROR(EOPNOTSUPP, "NFS-style lookups are not supported"));
        }

        error = fuse_internal_get_cached_vnode(mp, ino, flags, vpp);
        if (error || *vpp != NULL)
                return error;

        getnanouptime(&now);

        /* Do a LOOKUP, using nodeid as the parent and "." as filename */
        fdisp_init(&fdi, sizeof(dot));
        fdisp_make(&fdi, FUSE_LOOKUP, mp, nodeid, td, td->td_ucred);
        memcpy(fdi.indata, dot, sizeof(dot));
        error = fdisp_wait_answ(&fdi);

        if (error)
                goto out;

        feo = (struct fuse_entry_out *)fdi.answ;

        if (feo->nodeid == 0) {
                /* zero nodeid means ENOENT and cache it */
                error = ENOENT;
                goto out;
        }

        if (feo->nodeid != nodeid) {
                /*
                 * Something is very wrong with the server if "foo/." has a
                 * different inode number than "foo".
                 */
                static const char exterr[] = "Inconsistent LOOKUP response: "
                    "\"FILE/.\" has a different inode number than \"FILE\".";
                fuse_warn(data, FSESS_WARN_DOT_LOOKUP, exterr);
                error = EXTERROR(EIO, exterr);
                goto out;
        }

        vtyp = IFTOVT(feo->attr.mode);
        error = fuse_vnode_get(mp, feo, nodeid, NULL, vpp, NULL, vtyp);
        if (error)
                goto out;
        /* for last_local_modify and fuse_internal_cache_attrs */
        ASSERT_VOP_ELOCKED(*vpp, __func__);
        fvdat = VTOFUD(*vpp);

        if (timespeccmp(&now, &fvdat->last_local_modify, >)) {
                /*
                 * Attributes from the server are definitely newer than the
                 * last attributes we sent to the server, so cache them.
                 */
                fuse_internal_cache_attrs(*vpp, &feo->attr, feo->attr_valid,
                        feo->attr_valid_nsec, NULL, true);
        }
        fuse_validity_2_bintime(feo->entry_valid, feo->entry_valid_nsec,
                &fvdat->entry_cache_timeout);
out:
        fdisp_destroy(&fdi);
        return error;
}

static int
fuse_vfsop_root(struct mount *mp, int lkflags, struct vnode **vpp)
{
        struct fuse_data *data = fuse_get_mpdata(mp);
        int err = 0;

        if (data->vroot != NULL) {
                err = vget(data->vroot, lkflags);
                if (err == 0)
                        *vpp = data->vroot;
        } else {
                err = fuse_vnode_get(mp, NULL, FUSE_ROOT_ID, NULL, vpp, NULL,
                    VDIR);
                if (err == 0) {
                        FUSE_LOCK();
                        MPASS(data->vroot == NULL || data->vroot == *vpp);
                        if (data->vroot == NULL) {
                                SDT_PROBE2(fusefs, , vfsops, trace, 1,
                                        "new root vnode");
                                data->vroot = *vpp;
                                FUSE_UNLOCK();
                                vref(*vpp);
                        } else if (data->vroot != *vpp) {
                                SDT_PROBE2(fusefs, , vfsops, trace, 1,
                                        "root vnode race");
                                FUSE_UNLOCK();
                                vput(*vpp);
                                vrecycle(*vpp);
                                *vpp = data->vroot;
                        } else
                                FUSE_UNLOCK();
                }
        }
        return err;
}

static int
fuse_vfsop_statfs(struct mount *mp, struct statfs *sbp)
{
        struct fuse_dispatcher fdi;
        int err = 0;

        struct fuse_statfs_out *fsfo;
        struct fuse_data *data;

        data = fuse_get_mpdata(mp);

        if (!(data->dataflags & FSESS_INITED))
                goto fake;

        fdisp_init(&fdi, 0);
        fdisp_make(&fdi, FUSE_STATFS, mp, FUSE_ROOT_ID, NULL, NULL);
        err = fdisp_wait_answ(&fdi);
        if (err) {
                fdisp_destroy(&fdi);
                if (err == ENOTCONN) {
                        /*
                         * We want to seem a legitimate fs even if the daemon
                         * is stiff dead... (so that, eg., we can still do path
                         * based unmounting after the daemon dies).
                         */
                        goto fake;
                }
                return err;
        }
        fsfo = fdi.answ;

        sbp->f_blocks = fsfo->st.blocks;
        sbp->f_bfree = fsfo->st.bfree;
        sbp->f_bavail = fsfo->st.bavail;
        sbp->f_files = fsfo->st.files;
        sbp->f_ffree = fsfo->st.ffree;  /* cast from uint64_t to int64_t */
        sbp->f_namemax = fsfo->st.namelen;
        sbp->f_bsize = fsfo->st.frsize; /* cast from uint32_t to uint64_t */

        fdisp_destroy(&fdi);
        return 0;

fake:
        sbp->f_blocks = 0;
        sbp->f_bfree = 0;
        sbp->f_bavail = 0;
        sbp->f_files = 0;
        sbp->f_ffree = 0;
        sbp->f_namemax = 0;
        sbp->f_bsize = S_BLKSIZE;

        return 0;
}