FreeBSD/Linux Kernel Cross Reference
sys/fs/fuse/fuse_vfsops.c

     /*-
      * 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/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #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>
    
    #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, td);
           if ((err = namei(ndp)) != 0)
                   return err;
           NDFREE(ndp, NDF_ONLY_PNBUF);
           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 EOPNOTSUPP;
   
           error = VFS_VGET(mp, ffhp->nid, LK_EXCLUSIVE, &nvp);
           if (error) {
                   *vpp = NULLVP;
                   return (error);
           }
           fvdat = VTOFUD(nvp);
           if (fvdat->generation != ffhp->gen ) {
                   vput(nvp);
                   *vpp = NULLVP;
                   return (ESTALE);
           }
           *vpp = nvp;
           vnode_create_vobject(*vpp, 0, curthread);
           return (0);
   }
   
   static int
   fuse_vfsop_mount(struct mount *mp)
   {
           int err;
   
           uint64_t mntopts, __mntopts;
           uint32_t max_read;
           int daemon_timeout;
           int fd;
   
           size_t len;
   
           struct cdev *fdev;
           struct fuse_data *data = NULL;
           struct thread *td;
           struct file *fp, *fptmp;
           char *fspec, *subtype;
           struct vfsoptlist *opts;
   
           subtype = NULL;
           max_read = ~0;
           err = 0;
           mntopts = 0;
           __mntopts = 0;
           td = curthread;
   
           /* Get the new options passed to mount */
           opts = mp->mnt_optnew;
   
           if (!opts)
                   return EINVAL;
   
           /* `fspath' contains the mount point (eg. /mnt/fuse/sshfs); REQUIRED */
           if (!vfs_getopts(opts, "fspath", &err))
                   return err;
   
           /*
            * 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);
   
           (void)vfs_scanopt(opts, "max_read=", "%u", &max_read);
           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 err;
   
           /* `fd' contains the filedescriptor for this session; REQUIRED */
           if (vfs_scanopt(opts, "fd", "%d", &fd) != 1)
                   return EINVAL;
   
           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);
           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);
           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->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);
           }
           copystr(fspec, mp->mnt_stat.f_mntfromname, MNAMELEN - 1, &len);
           bzero(mp->mnt_stat.f_mntfromname + len, MNAMELEN - len);
           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_isimpl(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 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 (EOPNOTSUPP);
           }
   
           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)
                   return error;
   
           feo = (struct fuse_entry_out *)fdi.answ;
           if (feo->nodeid == 0) {
                   /* zero nodeid means ENOENT and cache it */
                   error = ENOENT;
                   goto out;
           }
   
           vtyp = IFTOVT(feo->attr.mode);
           error = fuse_vnode_get(mp, feo, nodeid, NULL, vpp, NULL, vtyp);
           if (error)
                   goto out;
           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, curthread);
                   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();
                                   VOP_UNLOCK(*vpp, 0);
                                   vrele(*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;
   }

Cache object: ed46cc0aa3b1953e6df5ca424046a007