/*-
 * 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/module.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/filio.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/queue.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/extattr.h>
#include <sys/stat.h>
#include <sys/unistd.h>
#include <sys/filedesc.h>
#include <sys/file.h>
#include <sys/fcntl.h>
#include <sys/dirent.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#define EXTERR_CATEGORY EXTERR_CAT_FUSE_VNOPS
#include <sys/exterrvar.h>
#include <sys/sysent.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>
#include <vm/vm_object.h>

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

#include <sys/priv.h>

/* Maximum number of hardlinks to a single FUSE file */
#define FUSE_LINK_MAX                      UINT32_MAX

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

/* vnode ops */
static vop_access_t fuse_vnop_access;
static vop_advlock_t fuse_vnop_advlock;
static vop_allocate_t fuse_vnop_allocate;
static vop_bmap_t fuse_vnop_bmap;
static vop_close_t fuse_fifo_close;
static vop_close_t fuse_vnop_close;
static vop_copy_file_range_t fuse_vnop_copy_file_range;
static vop_create_t fuse_vnop_create;
static vop_deallocate_t fuse_vnop_deallocate;
static vop_delayed_setsize_t fuse_vnop_delayed_setsize;
static vop_deleteextattr_t fuse_vnop_deleteextattr;
static vop_fdatasync_t fuse_vnop_fdatasync;
static vop_fsync_t fuse_vnop_fsync;
static vop_getattr_t fuse_vnop_getattr;
static vop_getextattr_t fuse_vnop_getextattr;
static vop_inactive_t fuse_vnop_inactive;
static vop_ioctl_t fuse_vnop_ioctl;
static vop_link_t fuse_vnop_link;
static vop_listextattr_t fuse_vnop_listextattr;
static vop_lookup_t fuse_vnop_lookup;
static vop_mkdir_t fuse_vnop_mkdir;
static vop_mknod_t fuse_vnop_mknod;
static vop_open_t fuse_vnop_open;
static vop_pathconf_t fuse_vnop_pathconf;
static vop_read_t fuse_vnop_read;
static vop_readdir_t fuse_vnop_readdir;
static vop_readlink_t fuse_vnop_readlink;
static vop_reclaim_t fuse_vnop_reclaim;
static vop_remove_t fuse_vnop_remove;
static vop_rename_t fuse_vnop_rename;
static vop_rmdir_t fuse_vnop_rmdir;
static vop_setattr_t fuse_vnop_setattr;
static vop_setextattr_t fuse_vnop_setextattr;
static vop_strategy_t fuse_vnop_strategy;
static vop_symlink_t fuse_vnop_symlink;
static vop_write_t fuse_vnop_write;
static vop_getpages_t fuse_vnop_getpages;
static vop_print_t fuse_vnop_print;
static vop_vptofh_t fuse_vnop_vptofh;

struct vop_vector fuse_fifoops = {
        .vop_default =          &fifo_specops,
        .vop_access =           fuse_vnop_access,
        .vop_close =            fuse_fifo_close,
        .vop_fsync =            fuse_vnop_fsync,
        .vop_getattr =          fuse_vnop_getattr,
        .vop_inactive =         fuse_vnop_inactive,
        .vop_pathconf =         fuse_vnop_pathconf,
        .vop_print =            fuse_vnop_print,
        .vop_read =             VOP_PANIC,
        .vop_reclaim =          fuse_vnop_reclaim,
        .vop_setattr =          fuse_vnop_setattr,
        .vop_write =            VOP_PANIC,
        .vop_vptofh =           fuse_vnop_vptofh,
};
VFS_VOP_VECTOR_REGISTER(fuse_fifoops);

struct vop_vector fuse_vnops = {
        .vop_allocate = fuse_vnop_allocate,
        .vop_default = &default_vnodeops,
        .vop_access = fuse_vnop_access,
        .vop_advlock = fuse_vnop_advlock,
        .vop_bmap = fuse_vnop_bmap,
        .vop_close = fuse_vnop_close,
        .vop_copy_file_range = fuse_vnop_copy_file_range,
        .vop_create = fuse_vnop_create,
        .vop_deallocate = fuse_vnop_deallocate,
        .vop_delayed_setsize = fuse_vnop_delayed_setsize,
        .vop_deleteextattr = fuse_vnop_deleteextattr,
        .vop_fsync = fuse_vnop_fsync,
        .vop_fdatasync = fuse_vnop_fdatasync,
        .vop_getattr = fuse_vnop_getattr,
        .vop_getextattr = fuse_vnop_getextattr,
        .vop_inactive = fuse_vnop_inactive,
        .vop_ioctl = fuse_vnop_ioctl,
        .vop_link = fuse_vnop_link,
        .vop_listextattr = fuse_vnop_listextattr,
        .vop_lookup = fuse_vnop_lookup,
        .vop_mkdir = fuse_vnop_mkdir,
        .vop_mknod = fuse_vnop_mknod,
        .vop_open = fuse_vnop_open,
        .vop_pathconf = fuse_vnop_pathconf,
        /*
         * TODO: implement vop_poll after upgrading to protocol 7.21.
         * FUSE_POLL was added in protocol 7.11, but it's kind of broken until
         * 7.21, which adds the ability for the client to choose which poll
         * events it wants, and for a client to deregister a file handle
         */
        .vop_read = fuse_vnop_read,
        .vop_readdir = fuse_vnop_readdir,
        .vop_readlink = fuse_vnop_readlink,
        .vop_reclaim = fuse_vnop_reclaim,
        .vop_remove = fuse_vnop_remove,
        .vop_rename = fuse_vnop_rename,
        .vop_rmdir = fuse_vnop_rmdir,
        .vop_setattr = fuse_vnop_setattr,
        .vop_setextattr = fuse_vnop_setextattr,
        .vop_strategy = fuse_vnop_strategy,
        .vop_symlink = fuse_vnop_symlink,
        .vop_write = fuse_vnop_write,
        .vop_getpages = fuse_vnop_getpages,
        .vop_print = fuse_vnop_print,
        .vop_vptofh = fuse_vnop_vptofh,
};
VFS_VOP_VECTOR_REGISTER(fuse_vnops);

/* Check permission for extattr operations, much like extattr_check_cred */
static int
fuse_extattr_check_cred(struct vnode *vp, int ns, struct ucred *cred,
        struct thread *td, accmode_t accmode)
{
        struct mount *mp = vnode_mount(vp);
        struct fuse_data *data = fuse_get_mpdata(mp);
        int default_permissions = data->dataflags & FSESS_DEFAULT_PERMISSIONS;

        /*
         * Kernel-invoked always succeeds.
         */
        if (cred == NOCRED)
                return (0);

        /*
         * Do not allow privileged processes in jail to directly manipulate
         * system attributes.
         */
        switch (ns) {
        case EXTATTR_NAMESPACE_SYSTEM:
                if (default_permissions) {
                        return (priv_check_cred(cred, PRIV_VFS_EXTATTR_SYSTEM));
                }
                return (0);
        case EXTATTR_NAMESPACE_USER:
                if (default_permissions) {
                        return (fuse_internal_access(vp, accmode, td, cred));
                }
                return (0);
        default:
                return (EPERM);
        }
}

/* Get a filehandle for a directory */
static int
fuse_filehandle_get_dir(struct vnode *vp, struct fuse_filehandle **fufhp,
        struct ucred *cred, pid_t pid)
{
        if (fuse_filehandle_get(vp, FREAD, fufhp, cred, pid) == 0)
                return 0;
        return fuse_filehandle_get(vp, FEXEC, fufhp, cred, pid);
}

/* Send FUSE_FLUSH for this vnode */
static int
fuse_flush(struct vnode *vp, struct ucred *cred, pid_t pid, int fflag)
{
        struct fuse_flush_in *ffi;
        struct fuse_filehandle *fufh;
        struct fuse_dispatcher fdi;
        struct thread *td = curthread;
        struct mount *mp = vnode_mount(vp);
        int err;

        if (fsess_not_impl(mp, FUSE_FLUSH))
                return 0;

        err = fuse_filehandle_getrw(vp, fflag, &fufh, cred, pid);
        if (err)
                return err;

        if (fufh->fuse_open_flags & FOPEN_NOFLUSH &&
            (!fsess_opt_writeback(mp)))
                return (0);

        fdisp_init(&fdi, sizeof(*ffi));
        fdisp_make_vp(&fdi, FUSE_FLUSH, vp, td, cred);
        ffi = fdi.indata;
        ffi->fh = fufh->fh_id;
        /* 
         * If the file has a POSIX lock then we're supposed to set lock_owner.
         * If not, then lock_owner is undefined.  So we may as well always set
         * it.
         */
        ffi->lock_owner = td->td_proc->p_pid;

        err = fdisp_wait_answ(&fdi);
        if (err == ENOSYS) {
                fsess_set_notimpl(mp, FUSE_FLUSH);
                err = 0;
        }
        fdisp_destroy(&fdi);
        return err;
}

/* Close wrapper for fifos.  */
static int
fuse_fifo_close(struct vop_close_args *ap)
{
        return (fifo_specops.vop_close(ap));
}

/* Invalidate a range of cached data, whether dirty of not */
static int
fuse_inval_buf_range(struct vnode *vp, off_t filesize, off_t start, off_t end)
{
        struct buf *bp;
        daddr_t left_lbn, end_lbn, right_lbn;
        off_t new_filesize;
        int iosize, left_on, right_on, right_blksize;

        iosize = fuse_iosize(vp);
        left_lbn = start / iosize;
        end_lbn = howmany(end, iosize);
        left_on = start & (iosize - 1);
        if (left_on != 0) {
                bp = getblk(vp, left_lbn, iosize, PCATCH, 0, 0);
                if ((bp->b_flags & B_CACHE) != 0 && bp->b_dirtyend >= left_on) {
                        /*
                         * Flush the dirty buffer, because we don't have a
                         * byte-granular way to record which parts of the
                         * buffer are valid.
                         */
                        bwrite(bp);
                        if (bp->b_error)
                                return (bp->b_error);
                } else {
                        brelse(bp);
                }
        }
        right_on = end & (iosize - 1);
        if (right_on != 0) {
                right_lbn = end / iosize;
                new_filesize = MAX(filesize, end);
                right_blksize = MIN(iosize, new_filesize - iosize * right_lbn);
                bp = getblk(vp, right_lbn, right_blksize, PCATCH, 0, 0);
                if ((bp->b_flags & B_CACHE) != 0 && bp->b_dirtyoff < right_on) {
                        /*
                         * Flush the dirty buffer, because we don't have a
                         * byte-granular way to record which parts of the
                         * buffer are valid.
                         */
                        bwrite(bp);
                        if (bp->b_error)
                                return (bp->b_error);
                } else {
                        brelse(bp);
                }
        }

        v_inval_buf_range(vp, left_lbn, end_lbn, iosize);
        return (0);
}

/* Send FUSE_IOCTL for this node */
static int
fuse_vnop_do_ioctl(struct vnode *vp, u_long cmd, void *arg, int fflag,
        struct ucred *cred, struct thread *td)
{
        struct fuse_dispatcher fdi;
        struct fuse_ioctl_in *fii;
        struct fuse_ioctl_out *fio;
        struct fuse_filehandle *fufh;
        uint32_t flags = 0;
        uint32_t insize = 0;
        uint32_t outsize = 0;
        int err;

        err = fuse_filehandle_getrw(vp, fflag, &fufh, cred, td->td_proc->p_pid);
        if (err != 0)
                return (err);

        if (vnode_isdir(vp)) {
                struct fuse_data *data = fuse_get_mpdata(vnode_mount(vp));

                if (!fuse_libabi_geq(data, 7, 18))
                        return (ENOTTY);
                flags |= FUSE_IOCTL_DIR;
        }
#ifdef __LP64__
#ifdef COMPAT_FREEBSD32
        if (SV_PROC_FLAG(td->td_proc, SV_ILP32))
                flags |= FUSE_IOCTL_32BIT;
#endif
#else /* !defined(__LP64__) */
        flags |= FUSE_IOCTL_32BIT;
#endif

        if ((cmd & IOC_OUT) != 0)
                outsize = IOCPARM_LEN(cmd);
        /* _IOWINT() sets IOC_VOID */
        if ((cmd & (IOC_VOID | IOC_IN)) != 0)
                insize = IOCPARM_LEN(cmd);

        fdisp_init(&fdi, sizeof(*fii) + insize);
        fdisp_make_vp(&fdi, FUSE_IOCTL, vp, td, cred);
        fii = fdi.indata;
        fii->fh = fufh->fh_id;
        fii->flags = flags;
        fii->cmd = cmd;
        fii->arg = (uintptr_t)arg;
        fii->in_size = insize;
        fii->out_size = outsize;
        if (insize > 0)
                memcpy((char *)fii + sizeof(*fii), arg, insize);

        err = fdisp_wait_answ(&fdi);
        if (err != 0) {
                if (err == ENOSYS)
                        err = ENOTTY;
                goto out;
        }

        fio = fdi.answ;
        if (fdi.iosize > sizeof(*fio)) {
                size_t realoutsize = fdi.iosize - sizeof(*fio);

                if (realoutsize > outsize) {
                        err = EIO;
                        goto out;
                }
                memcpy(arg, (char *)fio + sizeof(*fio), realoutsize);
        }
        if (fio->result > 0)
                td->td_retval[0] = fio->result;
        else
                err = -fio->result;

out:
        fdisp_destroy(&fdi);
        return (err);
}

/* Send FUSE_LSEEK for this node */
static int
fuse_vnop_do_lseek(struct vnode *vp, struct thread *td, struct ucred *cred,
        pid_t pid, off_t *offp, int whence)
{
        struct fuse_dispatcher fdi;
        struct fuse_filehandle *fufh;
        struct fuse_lseek_in *flsi;
        struct fuse_lseek_out *flso;
        struct mount *mp = vnode_mount(vp);
        int err;

        ASSERT_VOP_LOCKED(vp, __func__);

        err = fuse_filehandle_getrw(vp, FREAD, &fufh, cred, pid);
        if (err)
                return (err);
        fdisp_init(&fdi, sizeof(*flsi));
        fdisp_make_vp(&fdi, FUSE_LSEEK, vp, td, cred);
        flsi = fdi.indata;
        flsi->fh = fufh->fh_id;
        flsi->offset = *offp;
        flsi->whence = whence;
        err = fdisp_wait_answ(&fdi);
        if (err == ENOSYS) {
                fsess_set_notimpl(mp, FUSE_LSEEK);
        } else if (err == ENXIO) {
                /* Note: ENXIO means "no more hole/data regions until EOF" */
                fsess_set_impl(mp, FUSE_LSEEK);
        } else if (err == 0) {
                fsess_set_impl(mp, FUSE_LSEEK);
                flso = fdi.answ;
                *offp = flso->offset;
        }
        fdisp_destroy(&fdi);

        return (err);
}

/*
    struct vnop_access_args {
        struct vnode *a_vp;
#if VOP_ACCESS_TAKES_ACCMODE_T
        accmode_t a_accmode;
#else
        int a_mode;
#endif
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_access(struct vop_access_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int accmode = ap->a_accmode;
        struct ucred *cred = ap->a_cred;

        struct fuse_data *data = fuse_get_mpdata(vnode_mount(vp));

        int err;

        if (fuse_isdeadfs(vp)) {
                if (vnode_isvroot(vp)) {
                        return 0;
                }
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (!(data->dataflags & FSESS_INITED)) {
                if (vnode_isvroot(vp)) {
                        if (priv_check_cred(cred, PRIV_VFS_ADMIN) ||
                            (fuse_match_cred(data->daemoncred, cred) == 0)) {
                                return 0;
                        }
                }
                return (EXTERROR(EBADF, "Access denied until FUSE session "
                    "is initialized"));
        }
        if (vnode_islnk(vp)) {
                return 0;
        }

        err = fuse_internal_access(vp, accmode, ap->a_td, ap->a_cred);
        return err;
}

/*
 * struct vop_advlock_args {
 *      struct vop_generic_args a_gen;
 *      struct vnode *a_vp;
 *      void *a_id;
 *      int a_op;
 *      struct flock *a_fl;
 *      int a_flags;
 * }
 */
static int
fuse_vnop_advlock(struct vop_advlock_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct flock *fl = ap->a_fl;
        struct thread *td = curthread;
        struct ucred *cred = td->td_ucred;
        pid_t pid = td->td_proc->p_pid;
        struct fuse_filehandle *fufh;
        struct fuse_dispatcher fdi;
        struct fuse_lk_in *fli;
        struct fuse_lk_out *flo;
        struct vattr vattr;
        enum fuse_opcode op;
        off_t size, start;
        int dataflags, err;
        int flags = ap->a_flags;

        dataflags = fuse_get_mpdata(vnode_mount(vp))->dataflags;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }

        switch(ap->a_op) {
        case F_GETLK:
                op = FUSE_GETLK;
                break;
        case F_SETLK:
                if (flags & F_WAIT)
                        op = FUSE_SETLKW;
                else
                        op = FUSE_SETLK;
                break;
        case F_UNLCK:
                op = FUSE_SETLK;
                break;
        default:
                return (EXTERROR(EINVAL, "Unsupported lock flags"));
        }

        if (!(dataflags & FSESS_POSIX_LOCKS))
                return vop_stdadvlock(ap);
        /* FUSE doesn't properly support flock until protocol 7.17 */
        if (flags & F_FLOCK)
                return vop_stdadvlock(ap);

        vn_lock(vp, LK_SHARED | LK_RETRY);

        switch (fl->l_whence) {
        case SEEK_SET:
        case SEEK_CUR:
                /*
                 * Caller is responsible for adding any necessary offset
                 * when SEEK_CUR is used.
                 */
                start = fl->l_start;
                break;

        case SEEK_END:
                err = fuse_internal_getattr(vp, &vattr, cred, td);
                if (err)
                        goto out;
                size = vattr.va_size;
                if (size > OFF_MAX ||
                    (fl->l_start > 0 && size > OFF_MAX - fl->l_start)) {
                        err = EXTERROR(EOVERFLOW, "Offset is too large");
                        goto out;
                }
                start = size + fl->l_start;
                break;

        default:
                return (EXTERROR(EINVAL, "Unsupported offset type"));
        }

        err = fuse_filehandle_get_anyflags(vp, &fufh, cred, pid);
        if (err)
                goto out;

        fdisp_init(&fdi, sizeof(*fli));

        fdisp_make_vp(&fdi, op, vp, td, cred);
        fli = fdi.indata;
        fli->fh = fufh->fh_id;
        fli->owner = td->td_proc->p_pid;
        fli->lk.start = start;
        if (fl->l_len != 0)
                fli->lk.end = start + fl->l_len - 1;
        else
                fli->lk.end = INT64_MAX;
        fli->lk.type = fl->l_type;
        fli->lk.pid = td->td_proc->p_pid;

        err = fdisp_wait_answ(&fdi);
        fdisp_destroy(&fdi);

        if (err == 0 && op == FUSE_GETLK) {
                flo = fdi.answ;
                fl->l_type = flo->lk.type;
                fl->l_whence = SEEK_SET;
                if (flo->lk.type != F_UNLCK) {
                        fl->l_pid = flo->lk.pid;
                        fl->l_start = flo->lk.start;
                        if (flo->lk.end == INT64_MAX)
                                fl->l_len = 0;
                        else
                                fl->l_len = flo->lk.end - flo->lk.start + 1;
                        fl->l_start = flo->lk.start;
                }
        }

out:
        VOP_UNLOCK(vp);
        return err;
}

static int
fuse_vnop_allocate(struct vop_allocate_args *ap)
{
        struct vnode *vp = ap->a_vp;
        off_t *len = ap->a_len;
        off_t *offset = ap->a_offset;
        struct ucred *cred = ap->a_cred;
        struct fuse_filehandle *fufh;
        struct mount *mp = vnode_mount(vp);
        struct fuse_dispatcher fdi;
        struct fuse_fallocate_in *ffi;
        struct uio io;
        pid_t pid = curthread->td_proc->p_pid;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        off_t filesize;
        int err;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        switch (vp->v_type) {
        case VFIFO:
                return (ESPIPE);
        case VLNK:
        case VREG:
                break;
        default:
                return (ENODEV);
        }

        if (vfs_isrdonly(mp))
                return (EROFS);

        if (fsess_not_impl(mp, FUSE_FALLOCATE))
                return (EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "FUSE_FALLOCATE"));

        ASSERT_CACHED_ATTRS_LOCKED(vp);

        io.uio_offset = *offset;
        io.uio_resid = *len;
        err = vn_rlimit_fsize(vp, &io, curthread);
        if (err)
                return (err);

        err = fuse_filehandle_getrw(vp, FWRITE, &fufh, cred, pid);
        if (err)
                return (err);

        fuse_vnode_update(vp, FN_MTIMECHANGE | FN_CTIMECHANGE);

        err = fuse_vnode_size(vp, &filesize, cred, curthread);
        if (err)
                return (err);
        fuse_inval_buf_range(vp, filesize, *offset, *offset + *len);

        fdisp_init(&fdi, sizeof(*ffi));
        fdisp_make_vp(&fdi, FUSE_FALLOCATE, vp, curthread, cred);
        ffi = fdi.indata;
        ffi->fh = fufh->fh_id;
        ffi->offset = *offset;
        ffi->length = *len;
        ffi->mode = 0;
        err = fdisp_wait_answ(&fdi);

        if (err == ENOSYS) {
                fsess_set_notimpl(mp, FUSE_FALLOCATE);
                err = EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "FUSE_ALLOCATE");
        } else if (err == EOPNOTSUPP) {
                /*
                 * The file system server does not support FUSE_FALLOCATE with
                 * the supplied mode for this particular file.
                 */
                err = EXTERROR(EOPNOTSUPP, "This file can't be pre-allocated");
        } else if (!err) {
                *offset += *len;
                *len = 0;
                fuse_vnode_undirty_cached_timestamps(vp, false);
                fuse_internal_clear_suid_on_write(vp, cred, curthread);
                if (*offset > fvdat->cached_attrs.va_size) {
                        fuse_vnode_setsize(vp, *offset, false);
                        getnanouptime(&fvdat->last_local_modify);
                }
        }

        fdisp_destroy(&fdi);
        return (err);
}

/* {
        struct vnode *a_vp;
        daddr_t a_bn;
        struct bufobj **a_bop;
        daddr_t *a_bnp;
        int *a_runp;
        int *a_runb;
} */
static int
fuse_vnop_bmap(struct vop_bmap_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct bufobj **bo = ap->a_bop;
        struct thread *td = curthread;
        struct mount *mp;
        struct fuse_dispatcher fdi;
        struct fuse_bmap_in *fbi;
        struct fuse_bmap_out *fbo;
        struct fuse_data *data;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        uint64_t biosize;
        off_t fsize = VNOVAL;
        daddr_t lbn = ap->a_bn;
        daddr_t *pbn = ap->a_bnp;
        int *runp = ap->a_runp;
        int *runb = ap->a_runb;
        int error = 0;
        int maxrun;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }

        mp = vnode_mount(vp);
        data = fuse_get_mpdata(mp);
        biosize = fuse_iosize(vp);
        maxrun = MIN(vp->v_mount->mnt_iosize_max / biosize - 1,
                data->max_readahead_blocks);

        if (bo != NULL)
                *bo = &vp->v_bufobj;

        /*
         * The FUSE_BMAP operation does not include the runp and runb
         * variables, so we must guess.  Report nonzero contiguous runs so
         * cluster_read will combine adjacent reads.  It's worthwhile to reduce
         * upcalls even if we don't know the true physical layout of the file.
         * 
         * FUSE file systems may opt out of read clustering in two ways:
         * * mounting with -onoclusterr
         * * Setting max_readahead <= maxbcachebuf during FUSE_INIT
         */
        if (runb != NULL)
                *runb = MIN(lbn, maxrun);
        if (runp != NULL && maxrun == 0)
                *runp = 0;
        else if (runp != NULL) {
                /*
                 * If the file's size is cached, use that value to calculate
                 * runp, even if the cache is expired.  runp is only advisory,
                 * and the risk of getting it wrong is not worth the cost of
                 * another upcall.
                 */
                CACHED_ATTR_LOCK(vp);
                fsize = fvdat->cached_attrs.va_size;
                CACHED_ATTR_UNLOCK(vp);
                if (fsize == VNOVAL)
                        error = fuse_vnode_size(vp, &fsize, td->td_ucred, td);
                if (error == 0)
                        *runp = MIN(MAX(0, fsize / (off_t)biosize - lbn - 1),
                                    maxrun);
                else
                        *runp = 0;
        }

        if (fsess_maybe_impl(mp, FUSE_BMAP)) {
                fdisp_init(&fdi, sizeof(*fbi));
                fdisp_make_vp(&fdi, FUSE_BMAP, vp, td, td->td_ucred);
                fbi = fdi.indata;
                fbi->block = lbn;
                fbi->blocksize = biosize;
                error = fdisp_wait_answ(&fdi);
                if (error == ENOSYS) {
                        fdisp_destroy(&fdi);
                        fsess_set_notimpl(mp, FUSE_BMAP);
                        error = 0;
                } else {
                        fbo = fdi.answ;
                        if (error == 0 && pbn != NULL)
                                *pbn = fbo->block;
                        fdisp_destroy(&fdi);
                        return error;
                }
        }

        /* If the daemon doesn't support BMAP, make up a sensible default */
        if (pbn != NULL)
                *pbn = lbn * btodb(biosize);
        return (error);
}

/*
    struct vop_close_args {
        struct vnode *a_vp;
        int  a_fflag;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_close(struct vop_close_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct mount *mp = vnode_mount(vp);
        struct ucred *cred = ap->a_cred;
        int fflag = ap->a_fflag;
        struct thread *td;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        pid_t pid;
        int err = 0;

        /* NB: a_td will be NULL from some async kernel contexts */
        td = ap->a_td ? ap->a_td : curthread;
        pid = td->td_proc->p_pid;

        if (fuse_isdeadfs(vp))
                return 0;
        if (vnode_isdir(vp))
                return 0;
        if (fflag & IO_NDELAY)
                return 0;

        if (cred == NULL)
                cred = td->td_ucred;

        err = fuse_flush(vp, cred, pid, fflag);
        ASSERT_CACHED_ATTRS_LOCKED(vp); /* For fvdat->flag */
        if (err == 0 && (fvdat->flag & FN_ATIMECHANGE) && !vfs_isrdonly(mp)) {
                struct vattr vap;
                struct fuse_data *data;
                int dataflags;
                int access_e = 0;

                data = fuse_get_mpdata(mp);
                dataflags = data->dataflags;
                if (dataflags & FSESS_DEFAULT_PERMISSIONS) {
                        struct vattr va;

                        fuse_internal_getattr(vp, &va, cred, td);
                        access_e = vaccess(vp->v_type, va.va_mode, va.va_uid,
                            va.va_gid, VWRITE, cred);
                }
                if (access_e == 0) {
                        VATTR_NULL(&vap);
                        ASSERT_CACHED_ATTRS_LOCKED(vp);
                        vap.va_atime = fvdat->cached_attrs.va_atime;
                        /*
                         * Ignore errors setting when setting atime.  That
                         * should not cause close(2) to fail.
                         */
                        fuse_internal_setattr(vp, &vap, td, NULL);
                }
        }
        /* TODO: close the file handle, if we're sure it's no longer used */
        if ((fvdat->flag & FN_SIZECHANGE) != 0) {
                fuse_vnode_savesize(vp, cred, pid);
        }
        return err;
}

/*
   struct vop_copy_file_range_args {
        struct vop_generic_args a_gen;
        struct vnode *a_invp;
        off_t *a_inoffp;
        struct vnode *a_outvp;
        off_t *a_outoffp;
        size_t *a_lenp;
        unsigned int a_flags;
        struct ucred *a_incred;
        struct ucred *a_outcred;
        struct thread *a_fsizetd;
}
 */
static int
fuse_vnop_copy_file_range(struct vop_copy_file_range_args *ap)
{
        struct vnode *invp = ap->a_invp;
        struct vnode *outvp = ap->a_outvp;
        struct mount *mp = vnode_mount(invp);
        struct fuse_vnode_data *outfvdat = VTOFUD(outvp);
        struct fuse_dispatcher fdi;
        struct fuse_filehandle *infufh, *outfufh;
        struct fuse_copy_file_range_in *fcfri;
        struct ucred *incred = ap->a_incred;
        struct ucred *outcred = ap->a_outcred;
        struct fuse_write_out *fwo;
        struct thread *td;
        struct uio io;
        off_t outfilesize;
        ssize_t r = 0;
        pid_t pid;
        int err;

        if ((ap->a_flags & COPY_FILE_RANGE_CLONE) != 0)
                return (EXTERROR(ENOSYS, "Cannot clone"));

        if (mp == NULL || mp != vnode_mount(outvp))
                return (EXTERROR(ENOSYS, "Mount points do not match"));

        if (incred->cr_uid != outcred->cr_uid)
                return (EXTERROR(ENOSYS, "FUSE_COPY_FILE_RANGE does not "
                    "support different credentials for infd and outfd"));

        if (incred->cr_gid != outcred->cr_gid)
                return (EXTERROR(ENOSYS, "FUSE_COPY_FILE_RANGE does not "
                    "support different credentials for infd and outfd"));

        /* Caller busied mp, mnt_data can be safely accessed. */
        if (fsess_not_impl(mp, FUSE_COPY_FILE_RANGE))
                return (EXTERROR(ENOSYS, "This daemon does not "
                    "implement COPY_FILE_RANGE"));

        if (ap->a_fsizetd == NULL)
                td = curthread;
        else
                td = ap->a_fsizetd;
        pid = td->td_proc->p_pid;

        vn_lock_pair(invp, false, LK_SHARED, outvp, false, LK_EXCLUSIVE);
        if (invp->v_data == NULL || outvp->v_data == NULL) {
                err = EXTERROR(EBADF, "vnode got reclaimed");
                goto unlock;
        }

        err = fuse_filehandle_getrw(invp, FREAD, &infufh, incred, pid);
        if (err)
                goto unlock;

        err = fuse_filehandle_getrw(outvp, FWRITE, &outfufh, outcred, pid);
        if (err)
                goto unlock;

        io.uio_resid = *ap->a_lenp;
        if (ap->a_fsizetd) {
                io.uio_offset = *ap->a_outoffp;
                err = vn_rlimit_fsizex(outvp, &io, 0, &r, ap->a_fsizetd);
                if (err != 0)
                        goto unlock;
        }

        err = fuse_vnode_size(outvp, &outfilesize, outcred, curthread);
        if (err)
                goto unlock;

        vnode_pager_clean_sync(invp);
        err = fuse_inval_buf_range(outvp, outfilesize, *ap->a_outoffp,
                *ap->a_outoffp + io.uio_resid);
        if (err)
                goto unlock;

        fdisp_init(&fdi, sizeof(*fcfri));
        fdisp_make_vp(&fdi, FUSE_COPY_FILE_RANGE, invp, td, incred);
        fcfri = fdi.indata;
        fcfri->fh_in = infufh->fh_id;
        fcfri->off_in = *ap->a_inoffp;
        fcfri->nodeid_out = VTOI(outvp);
        fcfri->fh_out = outfufh->fh_id;
        fcfri->off_out = *ap->a_outoffp;
        fcfri->len = io.uio_resid;
        fcfri->flags = 0;

        err = fdisp_wait_answ(&fdi);
        if (err == 0) {
                fwo = fdi.answ;
                *ap->a_lenp = fwo->size;
                *ap->a_inoffp += fwo->size;
                *ap->a_outoffp += fwo->size;
                fuse_internal_clear_suid_on_write(outvp, outcred, td);
                ASSERT_CACHED_ATTRS_LOCKED(outvp);
                if (*ap->a_outoffp > outfvdat->cached_attrs.va_size) {
                        fuse_vnode_setsize(outvp, *ap->a_outoffp, false);
                        getnanouptime(&outfvdat->last_local_modify);
                }
                fuse_vnode_update(invp, FN_ATIMECHANGE);
                fuse_vnode_update(outvp, FN_MTIMECHANGE | FN_CTIMECHANGE);
        }
        fdisp_destroy(&fdi);

unlock:
        if (invp != outvp)
                VOP_UNLOCK(invp);
        VOP_UNLOCK(outvp);

        if (err == ENOSYS)
                fsess_set_notimpl(mp, FUSE_COPY_FILE_RANGE);

        /*
         * No need to call vn_rlimit_fsizex_res before return, since the uio is
         * local.
         */
        return (err);
}

static void
fdisp_make_mknod_for_fallback(
        struct fuse_dispatcher *fdip,
        struct componentname *cnp,
        struct vnode *dvp,
        uint64_t parentnid,
        struct thread *td,
        struct ucred *cred,
        mode_t mode,
        enum fuse_opcode *op)
{
        struct fuse_mknod_in *fmni;

        fdisp_init(fdip, sizeof(*fmni) + cnp->cn_namelen + 1);
        *op = FUSE_MKNOD;
        fdisp_make(fdip, *op, vnode_mount(dvp), parentnid, td, cred);
        fmni = fdip->indata;
        fmni->mode = mode;
        fmni->rdev = 0;
        memcpy((char *)fdip->indata + sizeof(*fmni), cnp->cn_nameptr,
            cnp->cn_namelen);
        ((char *)fdip->indata)[sizeof(*fmni) + cnp->cn_namelen] = '\0';
}
/*
    struct vnop_create_args {
        struct vnode *a_dvp;
        struct vnode **a_vpp;
        struct componentname *a_cnp;
        struct vattr *a_vap;
    };
*/
static int
fuse_vnop_create(struct vop_create_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        struct vattr *vap = ap->a_vap;
        struct thread *td = curthread;
        struct ucred *cred = cnp->cn_cred;

        struct fuse_data *data;
        struct fuse_create_in *fci;
        struct fuse_entry_out *feo;
        struct fuse_open_out *foo;
        struct fuse_dispatcher fdi, fdi2;
        struct fuse_dispatcher *fdip = &fdi;
        struct fuse_dispatcher *fdip2 = NULL;

        int err;

        struct mount *mp = vnode_mount(dvp);
        data = fuse_get_mpdata(mp);
        uint64_t parentnid = VTOFUD(dvp)->nid;
        mode_t mode = MAKEIMODE(vap->va_type, vap->va_mode);
        enum fuse_opcode op;
        int flags;

        if (fuse_isdeadfs(dvp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        /* FUSE expects sockets to be created with FUSE_MKNOD */
        if (vap->va_type == VSOCK)
                return fuse_internal_mknod(dvp, vpp, cnp, vap);

        /* 
         * VOP_CREATE doesn't tell us the open(2) flags, so we guess.  Only a
         * writable mode makes sense, and we might as well include readability
         * too.
         */
        flags = O_RDWR;

        bzero(&fdi, sizeof(fdi));

        if (vap->va_type != VREG)
                return (EXTERROR(EINVAL, "Only regular files can be created"));

        if (fsess_not_impl(mp, FUSE_CREATE) || vap->va_type == VSOCK) {
                /* Fallback to FUSE_MKNOD/FUSE_OPEN */
                fdisp_make_mknod_for_fallback(fdip, cnp, dvp, parentnid, td,
                        cred, mode, &op);
        } else {
                /* Use FUSE_CREATE */
                size_t insize;

                op = FUSE_CREATE;
                fdisp_init(fdip, sizeof(*fci) + cnp->cn_namelen + 1);
                fdisp_make(fdip, op, vnode_mount(dvp), parentnid, td, cred);
                fci = fdip->indata;
                fci->mode = mode;
                fci->flags = O_CREAT | flags;
                if (fuse_libabi_geq(data, 7, 12)) {
                        insize = sizeof(*fci);
                        fci->umask = td->td_proc->p_pd->pd_cmask;
                } else {
                        insize = sizeof(struct fuse_open_in);
                }

                memcpy((char *)fdip->indata + insize, cnp->cn_nameptr,
                    cnp->cn_namelen);
                ((char *)fdip->indata)[insize + cnp->cn_namelen] = '\0';
        }

        err = fdisp_wait_answ(fdip);

        if (err) {
                if (err == ENOSYS && op == FUSE_CREATE) {
                        fsess_set_notimpl(mp, FUSE_CREATE);
                        fdisp_destroy(fdip);
                        fdisp_make_mknod_for_fallback(fdip, cnp, dvp,
                                parentnid, td, cred, mode, &op);
                        err = fdisp_wait_answ(fdip);
                }
                if (err)
                        goto out;
        }

        feo = fdip->answ;

        if ((err = fuse_internal_checkentry(feo, vap->va_type))) {
                goto out;
        }

        if (op == FUSE_CREATE) {
                if (fuse_libabi_geq(data, 7, 9))
                        foo = (struct fuse_open_out*)(feo + 1);
                else
                        foo = (struct fuse_open_out*)((char*)feo +
                                FUSE_COMPAT_ENTRY_OUT_SIZE);
        } else {
                /* Issue a separate FUSE_OPEN */
                struct fuse_open_in *foi;

                fdip2 = &fdi2;
                fdisp_init(fdip2, sizeof(*foi));
                fdisp_make(fdip2, FUSE_OPEN, vnode_mount(dvp), feo->nodeid, td,
                        cred);
                foi = fdip2->indata;
                foi->flags = flags;
                err = fdisp_wait_answ(fdip2);
                if (err)
                        goto out;
                foo = fdip2->answ;
        }
        err = fuse_vnode_get(mp, feo, feo->nodeid, dvp, vpp, cnp, vap->va_type);
        if (err) {
                struct fuse_release_in *fri;
                uint64_t nodeid = feo->nodeid;
                uint64_t fh_id = foo->fh;

                fdisp_destroy(fdip);
                fdisp_init(fdip, sizeof(*fri));
                fdisp_make(fdip, FUSE_RELEASE, mp, nodeid, td, cred);
                fri = fdip->indata;
                fri->fh = fh_id;
                fri->flags = flags;
                fuse_insert_callback(fdip->tick, fuse_internal_forget_callback);
                fuse_insert_message(fdip->tick, false);
                goto out;
        }
        ASSERT_VOP_ELOCKED(*vpp, "fuse_vnop_create");
        fuse_internal_cache_attrs(*vpp, &feo->attr, feo->attr_valid,
                feo->attr_valid_nsec, NULL, true);

        fuse_filehandle_init(*vpp, FUFH_RDWR, NULL, td, cred, foo);
        fuse_vnode_open(*vpp, foo->open_flags, td);
        /* 
         * Purge the parent's attribute cache because the daemon should've
         * updated its mtime and ctime
         */
        fuse_vnode_clear_attr_cache(dvp);
        cache_purge_negative(dvp);

out:
        if (fdip2)
                fdisp_destroy(fdip2);
        fdisp_destroy(fdip);
        return err;
}

/*
    struct vnop_fdatasync_args {
        struct vop_generic_args a_gen;
        struct vnode * a_vp;
        struct thread * a_td;
    };
*/
static int
fuse_vnop_fdatasync(struct vop_fdatasync_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct thread *td = ap->a_td;
        int waitfor = MNT_WAIT;

        int err = 0;

        if (fuse_isdeadfs(vp)) {
                return 0;
        }
        if ((err = vop_stdfdatasync_buf(ap)))
                return err;

        return fuse_internal_fsync(vp, td, waitfor, true);
}

/*
    struct vnop_fsync_args {
        struct vop_generic_args a_gen;
        struct vnode * a_vp;
        int  a_waitfor;
        struct thread * a_td;
    };
*/
static int
fuse_vnop_fsync(struct vop_fsync_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct thread *td = ap->a_td;
        int waitfor = ap->a_waitfor;
        int err = 0;

        if (fuse_isdeadfs(vp)) {
                return 0;
        }
        if ((err = vop_stdfsync(ap)))
                return err;

        return fuse_internal_fsync(vp, td, waitfor, false);
}

/*
    struct vnop_getattr_args {
        struct vnode *a_vp;
        struct vattr *a_vap;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_getattr(struct vop_getattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vattr *vap = ap->a_vap;
        struct ucred *cred = ap->a_cred;
        struct thread *td = curthread;
        int err = 0;

        err = fuse_internal_getattr(vp, vap, cred, td);
        if (err == ENOTCONN && vnode_isvroot(vp)) {
                /*
                 * We want to seem a legitimate fs even if the daemon is dead,
                 * so that, eg., we can still do path based unmounting after
                 * the daemon dies.
                 */
                err = 0;
                bzero(vap, sizeof(*vap));
                vap->va_type = vnode_vtype(vp);
        }
        return err;
}

/*
    struct vnop_inactive_args {
        struct vnode *a_vp;
    };
*/
static int
fuse_vnop_inactive(struct vop_inactive_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct thread *td = curthread;

        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        struct fuse_filehandle *fufh, *fufh_tmp;

        int need_flush = 1;

        ASSERT_CACHED_ATTRS_LOCKED(vp); /* For fvdat->flag */
        LIST_FOREACH_SAFE(fufh, &fvdat->handles, next, fufh_tmp) {
                if (need_flush && vp->v_type == VREG) {
                        if ((VTOFUD(vp)->flag & FN_SIZECHANGE) != 0) {
                                fuse_vnode_savesize(vp, NULL, 0);
                        }
                        if ((fvdat->flag & FN_REVOKED) != 0)
                                fuse_io_invalbuf(vp, td);
                        else
                                fuse_io_flushbuf(vp, MNT_WAIT, td);
                        need_flush = 0;
                }
                fuse_filehandle_close(vp, fufh, td, NULL);
        }

        if ((fvdat->flag & FN_REVOKED) != 0)
                vrecycle(vp);

        return 0;
}

/*
    struct vnop_ioctl_args {
        struct vnode *a_vp;
        u_long a_command;
        caddr_t a_data;
        int a_fflag;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_ioctl(struct vop_ioctl_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct mount *mp = vnode_mount(vp);
        struct ucred *cred = ap->a_cred;
        struct thread *td = ap->a_td;
        int err;

        if (fuse_isdeadfs(vp)) {
                return (ENXIO);
        }

        switch (ap->a_command) {
        case FIOSEEKDATA:
        case FIOSEEKHOLE:
                /* Call FUSE_LSEEK, if we can, or fall back to vop_stdioctl */
                if (fsess_maybe_impl(mp, FUSE_LSEEK)) {
                        off_t *offp = ap->a_data;
                        pid_t pid = td->td_proc->p_pid;
                        int whence;

                        if (ap->a_command == FIOSEEKDATA)
                                whence = SEEK_DATA;
                        else
                                whence = SEEK_HOLE;

                        vn_lock(vp, LK_SHARED | LK_RETRY);
                        err = fuse_vnop_do_lseek(vp, td, cred, pid, offp,
                            whence);
                        VOP_UNLOCK(vp);
                }
                if (fsess_not_impl(mp, FUSE_LSEEK))
                        err = vop_stdioctl(ap);
                break;
        default:
                err = fuse_vnop_do_ioctl(vp, ap->a_command, ap->a_data,
                    ap->a_fflag, cred, td);
                break;
        }
        return (err);
}


/*
    struct vnop_link_args {
        struct vnode *a_tdvp;
        struct vnode *a_vp;
        struct componentname *a_cnp;
    };
*/
static int
fuse_vnop_link(struct vop_link_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *tdvp = ap->a_tdvp;
        struct componentname *cnp = ap->a_cnp;

        struct vattr *vap = VTOVA(vp);

        struct fuse_dispatcher fdi;
        struct fuse_entry_out *feo;
        struct fuse_link_in fli;

        int err;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (vnode_mount(tdvp) != vnode_mount(vp)) {
                return (EXDEV);
        }

        /*
         * This is a seatbelt check to protect naive userspace filesystems from
         * themselves and the limitations of the FUSE IPC protocol.  If a
         * filesystem does not allow attribute caching, assume it is capable of
         * validating that nlink does not overflow.
         */
        if (vap != NULL && vap->va_nlink >= FUSE_LINK_MAX)
                return (EMLINK);
        fli.oldnodeid = VTOI(vp);

        fdisp_init(&fdi, 0);
        fuse_internal_newentry_makerequest(vnode_mount(tdvp), VTOI(tdvp), cnp,
            FUSE_LINK, &fli, sizeof(fli), &fdi);
        if ((err = fdisp_wait_answ(&fdi))) {
                goto out;
        }
        feo = fdi.answ;

        if (fli.oldnodeid != feo->nodeid) {
                static const char exterr[] = "Server assigned wrong inode "
                    "for a hard link.";
                struct fuse_data *data = fuse_get_mpdata(vnode_mount(vp));
                fuse_warn(data, FSESS_WARN_ILLEGAL_INODE, exterr);
                fuse_vnode_clear_attr_cache(vp);
                fuse_vnode_clear_attr_cache(tdvp);
                err = EXTERROR(EIO, exterr);
                goto out;
        }

        err = fuse_internal_checkentry(feo, vnode_vtype(vp));
        if (!err) {
                /* 
                 * Purge the parent's attribute cache because the daemon
                 * should've updated its mtime and ctime
                 */
                fuse_vnode_clear_attr_cache(tdvp);
                fuse_internal_cache_attrs(vp, &feo->attr, feo->attr_valid,
                        feo->attr_valid_nsec, NULL, true);
        }
out:
        fdisp_destroy(&fdi);
        return err;
}

struct fuse_lookup_alloc_arg {
        struct fuse_entry_out *feo;
        struct componentname *cnp;
        uint64_t nid;
        __enum_uint8(vtype) vtyp;
};

/* Callback for vn_get_ino */
static int
fuse_lookup_alloc(struct mount *mp, void *arg, int lkflags, struct vnode **vpp)
{
        struct fuse_lookup_alloc_arg *flaa = arg;

        return fuse_vnode_get(mp, flaa->feo, flaa->nid, NULL, vpp, flaa->cnp,
                flaa->vtyp);
}

SDT_PROBE_DEFINE3(fusefs, , vnops, cache_lookup,
        "int", "struct timespec*", "struct timespec*");
/*
    struct vnop_lookup_args {
        struct vnodeop_desc *a_desc;
        struct vnode *a_dvp;
        struct vnode **a_vpp;
        struct componentname *a_cnp;
    };
*/
int
fuse_vnop_lookup(struct vop_lookup_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        struct thread *td = curthread;
        struct ucred *cred = cnp->cn_cred;
        struct timespec now;

        int nameiop = cnp->cn_nameiop;
        bool isdotdot = cnp->cn_flags & ISDOTDOT;
        bool islastcn = cnp->cn_flags & ISLASTCN;
        struct mount *mp = vnode_mount(dvp);
        struct fuse_data *data = fuse_get_mpdata(mp);
        int default_permissions = data->dataflags & FSESS_DEFAULT_PERMISSIONS;
        bool is_dot;

        int err = 0;
        int lookup_err = 0;
        struct vnode *vp = NULL;

        struct fuse_dispatcher fdi;
        bool did_lookup = false;
        struct fuse_entry_out *feo = NULL;
        __enum_uint8(vtype) vtyp;       /* vnode type of target */

        uint64_t nid;

        if (fuse_isdeadfs(dvp)) {
                *vpp = NULL;
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (!vnode_isdir(dvp))
                return ENOTDIR;

        if (islastcn && vfs_isrdonly(mp) && (nameiop != LOOKUP))
                return EROFS;

        if ((cnp->cn_flags & NOEXECCHECK) != 0)
                cnp->cn_flags &= ~NOEXECCHECK;
        else if ((err = fuse_internal_access(dvp, VEXEC, td, cred)))
                return err;

        ASSERT_CACHED_ATTRS_LOCKED(dvp);        /* For flag */
        is_dot = cnp->cn_namelen == 1 && *(cnp->cn_nameptr) == '.';
        if (isdotdot && !(data->dataflags & FSESS_EXPORT_SUPPORT)) {
                if (!(VTOFUD(dvp)->flag & FN_PARENT_NID)) {
                        /*
                         * Since the file system doesn't support ".." lookups,
                         * we have no way to find this entry.
                         */
                        return (EXTERROR(ESTALE, "This server does not support "
                            "'..' lookups"));
                }
                nid = VTOFUD(dvp)->parent_nid;
                if (nid == 0)
                        return ENOENT;
                /* .. is obviously a directory */
                vtyp = VDIR;
        } else if (is_dot) {
                nid = VTOI(dvp);
                /* . is obviously a directory */
                vtyp = VDIR;
        } else {
                struct timespec timeout;
                int ncpticks; /* here to accommodate for API contract */

                err = cache_lookup(dvp, vpp, cnp, &timeout, &ncpticks);
                getnanouptime(&now);
                SDT_PROBE3(fusefs, , vnops, cache_lookup, err, &timeout, &now);
                switch (err) {
                case -1:                /* positive match */
                        if (timespeccmp(&timeout, &now, >)) {
                                counter_u64_add(fuse_lookup_cache_hits, 1);
                        } else {
                                /* Cache timeout */
                                counter_u64_add(fuse_lookup_cache_misses, 1);
                                bintime_clear(
                                        &VTOFUD(*vpp)->entry_cache_timeout);
                                cache_purge(*vpp);
                                if (dvp != *vpp)
                                        vput(*vpp);
                                else 
                                        vrele(*vpp);
                                *vpp = NULL;
                                break;
                        }
                        return 0;

                case 0:         /* no match in cache */
                        counter_u64_add(fuse_lookup_cache_misses, 1);
                        break;

                case ENOENT:            /* negative match */
                        if (timespeccmp(&timeout, &now, <=)) {
                                /* Cache timeout */
                                cache_purge_negative(dvp);
                                break;
                        }
                        /* fall through */
                default:
                        return err;
                }

                fdisp_init(&fdi, cnp->cn_namelen + 1);
                fdisp_make(&fdi, FUSE_LOOKUP, mp, VTOI(dvp), td, cred);

                memcpy(fdi.indata, cnp->cn_nameptr, cnp->cn_namelen);
                ((char *)fdi.indata)[cnp->cn_namelen] = '\0';
                lookup_err = fdisp_wait_answ(&fdi);
                did_lookup = true;

                if (!lookup_err) {
                        /* lookup call succeeded */
                        feo = (struct fuse_entry_out *)fdi.answ;
                        nid = feo->nodeid;
                        if (nid == 0) {
                                /* zero nodeid means ENOENT and cache it */
                                struct timespec timeout;

                                fdi.answ_stat = ENOENT;
                                lookup_err = ENOENT;
                                if (cnp->cn_flags & MAKEENTRY) {
                                        fuse_validity_2_timespec(feo, &timeout);
                                        /* Use the same entry_time for .. as for
                                         * the file itself.  That doesn't honor
                                         * exactly what the fuse server tells
                                         * us, but to do otherwise would require
                                         * another cache lookup at this point.
                                         */
                                        struct timespec *dtsp = NULL;
                                        cache_enter_time(dvp, *vpp, cnp,
                                                &timeout, dtsp);
                                }
                        }
                        vtyp = IFTOVT(feo->attr.mode);
                }
                if (lookup_err && (!fdi.answ_stat || lookup_err != ENOENT)) {
                        fdisp_destroy(&fdi);
                        return lookup_err;
                }
        }
        /* lookup_err, if non-zero, must be ENOENT at this point */

        if (lookup_err) {
                /* Entry not found */
                if ((nameiop == CREATE || nameiop == RENAME) && islastcn) {
                        if (default_permissions)
                                err = fuse_internal_access(dvp, VWRITE, td,
                                    cred);
                        else
                                err = 0;
                        if (!err) {
                                err = EJUSTRETURN;
                        }
                } else {
                        err = ENOENT;
                }
        } else {
                /* Entry was found */
                if (isdotdot) {
                        struct fuse_lookup_alloc_arg flaa;

                        flaa.nid = nid;
                        flaa.feo = feo;
                        flaa.cnp = cnp;
                        flaa.vtyp = vtyp;
                        err = vn_vget_ino_gen(dvp, fuse_lookup_alloc, &flaa, 0,
                                &vp);
                        *vpp = vp;
                } else if (nid == VTOI(dvp)) {
                        if (is_dot) {
                                vref(dvp);
                                *vpp = dvp;
                        } else {
                                static const char exterr[] = "Server assigned "
                                    "same inode to both parent and child.";
                                fuse_warn(fuse_get_mpdata(mp),
                                    FSESS_WARN_ILLEGAL_INODE, exterr);
                                err = EXTERROR(EIO, exterr);
                        }

                } else {
                        struct fuse_vnode_data *fvdat;

                        err = fuse_vnode_get(vnode_mount(dvp), feo, nid, dvp,
                            &vp, cnp, vtyp);
                        if (err)
                                goto out;
                        *vpp = vp;
                        fvdat = VTOFUD(vp);

                        MPASS(feo != NULL);
                        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);

                        if ((nameiop == DELETE || nameiop == RENAME) &&
                                islastcn && default_permissions)
                        {
                                struct vattr dvattr;

                                err = fuse_internal_access(dvp, VWRITE, td,
                                        cred);
                                if (err != 0)
                                        goto out;
                                /* 
                                 * if the parent's sticky bit is set, check
                                 * whether we're allowed to remove the file.
                                 * Need to figure out the vnode locking to make
                                 * this work.
                                 */
                                fuse_internal_getattr(dvp, &dvattr, cred, td);
                                if ((dvattr.va_mode & S_ISTXT) &&
                                        fuse_internal_access(dvp, VADMIN, td,
                                                cred) &&
                                        fuse_internal_access(*vpp, VADMIN, td,
                                                cred)) {
                                        err = EPERM;
                                        goto out;
                                }
                        }
                }
        }
out:
        if (err) {
                if (vp != NULL && dvp != vp)
                        vput(vp);
                else if (vp != NULL)
                        vrele(vp);
                *vpp = NULL;
        }
        if (did_lookup)
                fdisp_destroy(&fdi);

        return err;
}

/*
    struct vnop_mkdir_args {
        struct vnode *a_dvp;
        struct vnode **a_vpp;
        struct componentname *a_cnp;
        struct vattr *a_vap;
    };
*/
static int
fuse_vnop_mkdir(struct vop_mkdir_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        struct vattr *vap = ap->a_vap;

        struct fuse_mkdir_in fmdi;

        if (fuse_isdeadfs(dvp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        fmdi.mode = MAKEIMODE(vap->va_type, vap->va_mode);
        fmdi.umask = curthread->td_proc->p_pd->pd_cmask;

        return (fuse_internal_newentry(dvp, vpp, cnp, FUSE_MKDIR, &fmdi,
            sizeof(fmdi), VDIR));
}

/*
    struct vnop_mknod_args {
        struct vnode *a_dvp;
        struct vnode **a_vpp;
        struct componentname *a_cnp;
        struct vattr *a_vap;
    };
*/
static int
fuse_vnop_mknod(struct vop_mknod_args *ap)
{

        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        struct vattr *vap = ap->a_vap;

        if (fuse_isdeadfs(dvp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        return fuse_internal_mknod(dvp, vpp, cnp, vap);
}

/*
    struct vop_open_args {
        struct vnode *a_vp;
        int  a_mode;
        struct ucred *a_cred;
        struct thread *a_td;
        int a_fdidx; / struct file *a_fp;
    };
*/
static int
fuse_vnop_open(struct vop_open_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int a_mode = ap->a_mode;
        struct thread *td = ap->a_td;
        struct ucred *cred = ap->a_cred;
        pid_t pid = td->td_proc->p_pid;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        if (VN_ISDEV(vp) || vp->v_type == VFIFO)
                return (EXTERROR(EOPNOTSUPP, "Unsupported vnode type",
                    vp->v_type));
        if ((a_mode & (FREAD | FWRITE | FEXEC)) == 0)
                return (EXTERROR(EINVAL, "Illegal mode", a_mode));

        if (fuse_filehandle_validrw(vp, a_mode, cred, pid)) {
                fuse_vnode_open(vp, 0, td);
                return 0;
        }

        return fuse_filehandle_open(vp, a_mode, NULL, td, cred);
}

static int
fuse_vnop_pathconf(struct vop_pathconf_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct mount *mp;
        struct fuse_filehandle *fufh;
        int err;
        bool closefufh = false;

        switch (ap->a_name) {
        case _PC_FILESIZEBITS:
                *ap->a_retval = 64;
                return (0);
        case _PC_NAME_MAX:
                *ap->a_retval = NAME_MAX;
                return (0);
        case _PC_LINK_MAX:
                *ap->a_retval = MIN(LONG_MAX, FUSE_LINK_MAX);
                return (0);
        case _PC_SYMLINK_MAX:
                *ap->a_retval = MAXPATHLEN;
                return (0);
        case _PC_NO_TRUNC:
                *ap->a_retval = 1;
                return (0);
        case _PC_MIN_HOLE_SIZE:
                /*
                 * The FUSE protocol provides no mechanism for a server to
                 * report _PC_MIN_HOLE_SIZE.  It's a protocol bug.  Instead,
                 * return EINVAL if the server does not support FUSE_LSEEK, or
                 * 1 if it does.
                 */
                mp = vnode_mount(vp);
                if (!fsess_is_impl(mp, FUSE_LSEEK) &&
                    !fsess_not_impl(mp, FUSE_LSEEK)) {
                        off_t offset = 0;

                        /*
                         * Issue a FUSE_LSEEK to find out if it's supported.
                         * Use SEEK_DATA instead of SEEK_HOLE, because the
                         * latter generally requires sequential scans of file
                         * metadata, which can be slow.
                         */
                        err = fuse_vnop_do_lseek(vp, curthread,
                            curthread->td_ucred, curthread->td_proc->p_pid,
                            &offset, SEEK_DATA);
                        if (err == EBADF) {
                                /*
                                 * pathconf() doesn't necessarily open the
                                 * file.  So we may need to do it here.
                                 */
                                err = fuse_filehandle_open(vp, FREAD, &fufh,
                                    curthread, curthread->td_ucred);
                                if (err == 0) {
                                        closefufh = true;
                                        err = fuse_vnop_do_lseek(vp, curthread,
                                            curthread->td_ucred,
                                            curthread->td_proc->p_pid, &offset,
                                            SEEK_DATA);
                                }
                                if (closefufh)
                                        fuse_filehandle_close(vp, fufh,
                                            curthread, curthread->td_ucred);
                        }

                }

                if (fsess_is_impl(mp, FUSE_LSEEK)) {
                        *ap->a_retval = 1;
                        return (0);
                } else if (fsess_not_impl(mp, FUSE_LSEEK)) {
                        /* FUSE_LSEEK is not implemented */
                        return (EXTERROR(EINVAL, "This server does not "
                            "implement FUSE_LSEEK"));
                } else {
                        return (err);
                }
        default:
                return (vop_stdpathconf(ap));
        }
}

SDT_PROBE_DEFINE3(fusefs, , vnops, filehandles_closed, "struct vnode*",
    "struct uio*", "struct ucred*");
/*
    struct vnop_read_args {
        struct vnode *a_vp;
        struct uio *a_uio;
        int  a_ioflag;
        struct ucred *a_cred;
    };
*/
static int
fuse_vnop_read(struct vop_read_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        int ioflag = ap->a_ioflag;
        struct ucred *cred = ap->a_cred;
        pid_t pid = curthread->td_proc->p_pid;
        struct fuse_filehandle *fufh;
        int err;
        bool closefufh = false, directio;

        MPASS(vp->v_type == VREG || vp->v_type == VDIR);

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }

        /*
         * XXX Check this flag without the lock.  See
         * https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293088
         */
        if (VTOFUD(vp)->flag & FN_DIRECTIO) {
                ioflag |= IO_DIRECT;
        }

        err = fuse_filehandle_getrw(vp, FREAD, &fufh, cred, pid);
        if (err == EBADF && vnode_mount(vp)->mnt_flag & MNT_EXPORTED) {
                /*
                 * nfsd will do I/O without first doing VOP_OPEN.  We
                 * must implicitly open the file here
                 */
                err = fuse_filehandle_open(vp, FREAD, &fufh, curthread, cred);
                closefufh = true;
        }
        if (err) {
                SDT_PROBE3(fusefs, , vnops, filehandles_closed, vp, uio, cred);
                return err;
        }

        /*
         * Ideally, when the daemon asks for direct io at open time, the
         * standard file flag should be set according to this, so that would
         * just change the default mode, which later on could be changed via
         * fcntl(2).
         * But this doesn't work, the O_DIRECT flag gets cleared at some point
         * (don't know where). So to make any use of the Fuse direct_io option,
         * we hardwire it into the file's private data (similarly to Linux,
         * btw.).
         */
        directio = (ioflag & IO_DIRECT) || !fsess_opt_datacache(vnode_mount(vp));

        fuse_vnode_update(vp, FN_ATIMECHANGE);
        if (directio) {
                SDT_PROBE2(fusefs, , vnops, trace, 1, "direct read of vnode");
                err = fuse_read_directbackend(vp, uio, cred, fufh);
        } else {
                SDT_PROBE2(fusefs, , vnops, trace, 1, "buffered read of vnode");
                err = fuse_read_biobackend(vp, uio, ioflag, cred, fufh, pid);
        }

        if (closefufh)
                fuse_filehandle_close(vp, fufh, curthread, cred);

        return (err);
}

/*
    struct vnop_readdir_args {
        struct vnode *a_vp;
        struct uio *a_uio;
        struct ucred *a_cred;
        int *a_eofflag;
        int *a_ncookies;
        uint64_t **a_cookies;
    };
*/
static int
fuse_vnop_readdir(struct vop_readdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct ucred *cred = ap->a_cred;
        struct fuse_filehandle *fufh = NULL;
        struct mount *mp = vnode_mount(vp);
        struct fuse_iov cookediov;
        int err = 0;
        uint64_t *cookies;
        ssize_t tresid;
        int ncookies;
        bool closefufh = false;
        pid_t pid = curthread->td_proc->p_pid;

        if (ap->a_eofflag)
                *ap->a_eofflag = 0;
        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (uio_resid(uio) < sizeof(struct dirent))
                return (EXTERROR(EINVAL, "Buffer is too small"));

        tresid = uio->uio_resid;
        err = fuse_filehandle_get_dir(vp, &fufh, cred, pid);
        if (err == EBADF && mp->mnt_flag & MNT_EXPORTED) {
                KASSERT(!fsess_is_impl(mp, FUSE_OPENDIR),
                        ("FUSE file systems that implement "
                         "FUSE_OPENDIR should not be exported"));
                /* 
                 * nfsd will do VOP_READDIR without first doing VOP_OPEN.  We
                 * must implicitly open the directory here.
                 */
                err = fuse_filehandle_open(vp, FREAD, &fufh, curthread, cred);
                closefufh = true;
        }
        if (err)
                return (err);
        if (ap->a_ncookies != NULL) {
                ncookies = uio->uio_resid /
                        (offsetof(struct dirent, d_name) + 4) + 1;
                cookies = malloc(ncookies * sizeof(*cookies), M_TEMP, M_WAITOK);
                *ap->a_ncookies = ncookies;
                *ap->a_cookies = cookies;
        } else {
                ncookies = 0;
                cookies = NULL;
        }
#define DIRCOOKEDSIZE FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET + MAXNAMLEN + 1)
        fiov_init(&cookediov, DIRCOOKEDSIZE);

        err = fuse_internal_readdir(vp, uio, fufh, &cookediov,
                &ncookies, cookies);

        fiov_teardown(&cookediov);
        if (closefufh)
                fuse_filehandle_close(vp, fufh, curthread, cred);

        if (ap->a_ncookies != NULL) {
                if (err == 0) {
                        *ap->a_ncookies -= ncookies;
                } else {
                        free(*ap->a_cookies, M_TEMP);
                        *ap->a_ncookies = 0;
                        *ap->a_cookies = NULL;
                }
        }
        if (err == 0 && tresid == uio->uio_resid)
                *ap->a_eofflag = 1;

        return err;
}

/*
    struct vnop_readlink_args {
        struct vnode *a_vp;
        struct uio *a_uio;
        struct ucred *a_cred;
    };
*/
static int
fuse_vnop_readlink(struct vop_readlink_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct ucred *cred = ap->a_cred;

        struct fuse_dispatcher fdi;
        int err;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (!vnode_islnk(vp)) {
                return EINVAL;
        }
        fdisp_init(&fdi, 0);
        err = fdisp_simple_putget_vp(&fdi, FUSE_READLINK, vp, curthread, cred);
        if (err) {
                goto out;
        }
        if (strnlen(fdi.answ, fdi.iosize) + 1 < fdi.iosize) {
                static const char exterr[] = "Server returned an embedded NUL "
                    "from FUSE_READLINK.";
                struct fuse_data *data = fuse_get_mpdata(vnode_mount(vp));
                fuse_warn(data, FSESS_WARN_READLINK_EMBEDDED_NUL, exterr);
                err = EXTERROR(EIO, exterr);
                goto out;
        }
        if (((char *)fdi.answ)[0] == '/' &&
            fuse_get_mpdata(vnode_mount(vp))->dataflags & FSESS_PUSH_SYMLINKS_IN) {
                char *mpth = vnode_mount(vp)->mnt_stat.f_mntonname;

                err = uiomove(mpth, strlen(mpth), uio);
        }
        if (!err) {
                err = uiomove(fdi.answ, fdi.iosize, uio);
        }
out:
        fdisp_destroy(&fdi);
        return err;
}

/*
    struct vnop_reclaim_args {
        struct vnode *a_vp;
    };
*/
static int
fuse_vnop_reclaim(struct vop_reclaim_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct thread *td = curthread;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        struct fuse_filehandle *fufh, *fufh_tmp;

        if (!fvdat) {
                panic("FUSE: no vnode data during recycling");
        }
        LIST_FOREACH_SAFE(fufh, &fvdat->handles, next, fufh_tmp) {
                printf("FUSE: vnode being reclaimed with open fufh "
                        "(type=%#x)", fufh->fufh_type);
                fuse_filehandle_close(vp, fufh, td, NULL);
        }

        if (VTOI(vp) == 1) {
                /*
                 * Don't send FUSE_FORGET for the root inode, because
                 * we never send FUSE_LOOKUP for it (see
                 * fuse_vfsop_root) and we don't want the server to see
                 * mismatched lookup counts.
                 */
                struct fuse_data *data;
                struct vnode *vroot;

                data = fuse_get_mpdata(vnode_mount(vp));
                FUSE_LOCK();
                vroot = data->vroot;
                data->vroot = NULL;
                FUSE_UNLOCK();
                if (vroot)
                        vrele(vroot);
        } else if (!fuse_isdeadfs(vp) && fvdat->nlookup > 0) {
                fuse_internal_forget_send(vnode_mount(vp), td, NULL, VTOI(vp),
                    fvdat->nlookup);
        }
        cache_purge(vp);
        vfs_hash_remove(vp);
        fuse_vnode_destroy(vp);

        return 0;
}

/*
    struct vnop_remove_args {
        struct vnode *a_dvp;
        struct vnode *a_vp;
        struct componentname *a_cnp;
    };
*/
static int
fuse_vnop_remove(struct vop_remove_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode *vp = ap->a_vp;
        struct componentname *cnp = ap->a_cnp;

        int err;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (vnode_isdir(vp)) {
                return (EXTERROR(EPERM, "vnode is a directory"));
        }

        err = fuse_internal_remove(dvp, vp, cnp, FUSE_UNLINK);

        return err;
}

SDT_PROBE_DEFINE4(fusefs, , vnops, erelookup, "struct vnode*",
        "struct vnode*", "struct vnode*", "struct vnode*");
/*
    struct vnop_rename_args {
        struct vnode *a_fdvp;
        struct vnode *a_fvp;
        struct componentname *a_fcnp;
        struct vnode *a_tdvp;
        struct vnode *a_tvp;
        struct componentname *a_tcnp;
    };
*/
static int
fuse_vnop_rename(struct vop_rename_args *ap)
{
        struct vnode *fdvp = ap->a_fdvp;
        struct vnode *fvp = ap->a_fvp;
        struct componentname *fcnp = ap->a_fcnp;
        struct vnode *tdvp = ap->a_tdvp;
        struct vnode *tvp = ap->a_tvp;
        struct componentname *tcnp = ap->a_tcnp;
        struct fuse_data *data;
        bool newparent = fdvp != tdvp;
        bool isdir = fvp->v_type == VDIR;
        int locktype;
        int err = 0;

        if (fuse_isdeadfs(fdvp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (fvp->v_mount != tdvp->v_mount ||
            (tvp && fvp->v_mount != tvp->v_mount)) {
                SDT_PROBE2(fusefs, , vnops, trace, 1, "cross-device rename");
                err = EXTERROR(EXDEV, "Cross-device rename");
                goto out;
        }
        if (ap->a_flags != 0) {
                err = EOPNOTSUPP;
                goto out;
        }
        cache_purge(fvp);

        /*
         * FUSE library is expected to check if target directory is not
         * under the source directory in the file system tree.
         * Linux performs this check at VFS level.
         */
        /* 
         * If source is a directory, and it will get a new parent, user must
         * have write permission to it, so ".." can be modified.
         */
        data = fuse_get_mpdata(vnode_mount(tdvp));

        if (tdvp != fdvp)
                locktype = LK_EXCLUSIVE; /* for fuse_vnode_setparent */
        else
                locktype = LK_SHARED;

        /*
         * Must use LK_NOWAIT to prevent LORs between fvp and tdvp or
         * tvp
         */
        if (vn_lock(fvp, locktype | LK_NOWAIT) != 0) {
                /*
                 * Can't release tdvp or tvp to try avoiding the LOR.
                 * Must return instead.
                 */
                SDT_PROBE4(fusefs, , vnops, erelookup, fdvp, fvp, tdvp,
                        tvp);
                err = ERELOOKUP;
                goto out;
        }

        if (data->dataflags & FSESS_DEFAULT_PERMISSIONS && isdir && newparent) {
                err = fuse_internal_access(fvp, VWRITE,
                        curthread, tcnp->cn_cred);
                if (err)
                        goto unlock;
        }
        err = fuse_internal_rename(fdvp, fcnp, tdvp, tcnp);
        if (err == 0) {
                if (tdvp != fdvp)
                        fuse_vnode_setparent(fvp, tdvp);
                if (tvp != NULL)
                        fuse_vnode_setparent(tvp, NULL);
        }

        if (tvp != NULL && tvp != fvp) {
                cache_purge(tvp);
        }
        if (vnode_isdir(fvp)) {
                if (((tvp != NULL) && vnode_isdir(tvp)) || vnode_isdir(fvp)) {
                        cache_purge(tdvp);
                }
                cache_purge(fdvp);
        }
unlock:
        VOP_UNLOCK(fvp);
out:
        if (tdvp == tvp) {
                vrele(tdvp);
        } else {
                vput(tdvp);
        }
        if (tvp != NULL) {
                vput(tvp);
        }
        vrele(fdvp);
        vrele(fvp);

        return err;
}

/*
    struct vnop_rmdir_args {
            struct vnode *a_dvp;
            struct vnode *a_vp;
            struct componentname *a_cnp;
    } *ap;
*/
static int
fuse_vnop_rmdir(struct vop_rmdir_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode *vp = ap->a_vp;

        int err;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        if (VTOFUD(vp) == VTOFUD(dvp)) {
                return (EXTERROR(EINVAL, "Directory to be removed "
                    "contains itself"));
        }
        err = fuse_internal_remove(dvp, vp, ap->a_cnp, FUSE_RMDIR);

        return err;
}

/*
    struct vnop_setattr_args {
        struct vnode *a_vp;
        struct vattr *a_vap;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_setattr(struct vop_setattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vattr *vap = ap->a_vap;
        struct ucred *cred = ap->a_cred;
        struct thread *td = curthread;
        struct mount *mp;
        struct fuse_data *data;
        struct vattr old_va;
        int dataflags;
        int err = 0, err2;
        accmode_t accmode = 0;
        bool checkperm;
        bool drop_suid = false;

        mp = vnode_mount(vp);
        data = fuse_get_mpdata(mp);
        dataflags = data->dataflags;
        checkperm = dataflags & FSESS_DEFAULT_PERMISSIONS;

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }

        if (vap->va_uid != (uid_t)VNOVAL) {
                if (checkperm) {
                        /* Only root may change a file's owner */
                        err = priv_check_cred(cred, PRIV_VFS_CHOWN);
                        if (err) {
                                /* As a special case, allow the null chown */
                                err2 = fuse_internal_getattr(vp, &old_va, cred,
                                        td);
                                if (err2)
                                        return (err2);
                                if (vap->va_uid != old_va.va_uid)
                                        return err;
                                drop_suid = true;
                        }
                }
                accmode |= VADMIN;
        }
        if (vap->va_gid != (gid_t)VNOVAL) {
                if (checkperm && priv_check_cred(cred, PRIV_VFS_CHOWN))
                        drop_suid = true;
                if (checkperm && !groupmember(vap->va_gid, cred)) {
                        /*
                         * Non-root users may only chgrp to one of their own
                         * groups 
                         */
                        err = priv_check_cred(cred, PRIV_VFS_CHOWN);
                        if (err) {
                                /* As a special case, allow the null chgrp */
                                err2 = fuse_internal_getattr(vp, &old_va, cred,
                                        td);
                                if (err2)
                                        return (err2);
                                if (vap->va_gid != old_va.va_gid)
                                        return err;
                        }
                }
                accmode |= VADMIN;
        }
        if (vap->va_size != VNOVAL) {
                switch (vp->v_type) {
                case VDIR:
                        return (EISDIR);
                case VLNK:
                case VREG:
                        if (vfs_isrdonly(mp))
                                return (EROFS);
                        err = vn_rlimit_trunc(vap->va_size, td);
                        if (err)
                                return (err);
                        break;
                default:
                        /*
                         * According to POSIX, the result is unspecified
                         * for file types other than regular files,
                         * directories and shared memory objects.  We
                         * don't support shared memory objects in the file
                         * system, and have dubious support for truncating
                         * symlinks.  Just ignore the request in other cases.
                         */
                        return (0);
                }
                /* Don't set accmode.  Permission to trunc is checked upstack */
        }
        if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
                if (vap->va_vaflags & VA_UTIMES_NULL)
                        accmode |= VWRITE;
                else
                        accmode |= VADMIN;
        }
        if (drop_suid) {
                if (vap->va_mode != (mode_t)VNOVAL)
                        vap->va_mode &= ~(S_ISUID | S_ISGID);
                else {
                        err = fuse_internal_getattr(vp, &old_va, cred, td);
                        if (err)
                                return (err);
                        vap->va_mode = old_va.va_mode & ~(S_ISUID | S_ISGID);
                }
        }
        if (vap->va_mode != (mode_t)VNOVAL) {
                /* Only root may set the sticky bit on non-directories */
                if (checkperm && vp->v_type != VDIR && (vap->va_mode & S_ISTXT)
                    && priv_check_cred(cred, PRIV_VFS_STICKYFILE))
                        return EFTYPE;
                if (checkperm && (vap->va_mode & S_ISGID)) {
                        err = fuse_internal_getattr(vp, &old_va, cred, td);
                        if (err)
                                return (err);
                        if (!groupmember(old_va.va_gid, cred)) {
                                err = priv_check_cred(cred, PRIV_VFS_SETGID);
                                if (err)
                                        return (err);
                        }
                }
                accmode |= VADMIN;
        }

        if (vfs_isrdonly(mp))
                return EROFS;

        if (checkperm) {
                err = fuse_internal_access(vp, accmode, td, cred);
        } else {
                err = 0;
        }
        if (err)
                return err;
        else
                return fuse_internal_setattr(vp, vap, td, cred);
}

/*
    struct vnop_strategy_args {
        struct vnode *a_vp;
        struct buf *a_bp;
    };
*/
static int
fuse_vnop_strategy(struct vop_strategy_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct buf *bp = ap->a_bp;

        if (!vp || fuse_isdeadfs(vp)) {
                bp->b_ioflags |= BIO_ERROR;
                bp->b_error = ENXIO;
                bufdone(bp);
                return 0;
        }

        /*
         * VOP_STRATEGY always returns zero and signals error via bp->b_ioflags.
         * fuse_io_strategy sets bp's error fields
         */
        (void)fuse_io_strategy(vp, bp);

        return 0;
}

/*
    struct vnop_symlink_args {
        struct vnode *a_dvp;
        struct vnode **a_vpp;
        struct componentname *a_cnp;
        struct vattr *a_vap;
        char *a_target;
    };
*/
static int
fuse_vnop_symlink(struct vop_symlink_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        const char *target = ap->a_target;

        struct fuse_dispatcher fdi;

        int err;
        size_t len;

        if (fuse_isdeadfs(dvp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }
        /*
         * Unlike the other creator type calls, here we have to create a message
         * where the name of the new entry comes first, and the data describing
         * the entry comes second.
         * Hence we can't rely on our handy fuse_internal_newentry() routine,
         * but put together the message manually and just call the core part.
         */

        len = strlen(target) + 1;
        fdisp_init(&fdi, len + cnp->cn_namelen + 1);
        fdisp_make_vp(&fdi, FUSE_SYMLINK, dvp, curthread, NULL);

        memcpy(fdi.indata, cnp->cn_nameptr, cnp->cn_namelen);
        ((char *)fdi.indata)[cnp->cn_namelen] = '\0';
        memcpy((char *)fdi.indata + cnp->cn_namelen + 1, target, len);

        err = fuse_internal_newentry_core(dvp, vpp, cnp, VLNK, &fdi);
        fdisp_destroy(&fdi);
        return err;
}

/*
    struct vnop_write_args {
        struct vnode *a_vp;
        struct uio *a_uio;
        int  a_ioflag;
        struct ucred *a_cred;
    };
*/
static int
fuse_vnop_write(struct vop_write_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        struct uio *uio = ap->a_uio;
        int ioflag = ap->a_ioflag;
        struct ucred *cred = ap->a_cred;
        pid_t pid = curthread->td_proc->p_pid;
        struct fuse_filehandle *fufh;
        int err;
        bool closefufh = false, directio;

        MPASS(vp->v_type == VREG || vp->v_type == VDIR);

        if (fuse_isdeadfs(vp)) {
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));
        }

        /*
         * XXX Check this flag without the lock.  See
         * https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293088
         */
        if (fvdat->flag & FN_DIRECTIO)
                ioflag |= IO_DIRECT;

        err = fuse_filehandle_getrw(vp, FWRITE, &fufh, cred, pid);
        if (err == EBADF && vnode_mount(vp)->mnt_flag & MNT_EXPORTED) {
                /*
                 * nfsd will do I/O without first doing VOP_OPEN.  We
                 * must implicitly open the file here
                 */
                err = fuse_filehandle_open(vp, FWRITE, &fufh, curthread, cred);
                closefufh = true;
        }
        if (err) {
                SDT_PROBE3(fusefs, , vnops, filehandles_closed, vp, uio, cred);
                return err;
        }

        /*
         * Ideally, when the daemon asks for direct io at open time, the
         * standard file flag should be set according to this, so that would
         * just change the default mode, which later on could be changed via
         * fcntl(2).
         * But this doesn't work, the O_DIRECT flag gets cleared at some point
         * (don't know where). So to make any use of the Fuse direct_io option,
         * we hardwire it into the file's private data (similarly to Linux,
         * btw.).
         */
        directio = (ioflag & IO_DIRECT) || !fsess_opt_datacache(vnode_mount(vp));

        fuse_vnode_update(vp, FN_MTIMECHANGE | FN_CTIMECHANGE);
        if (directio) {
                off_t start, end, filesize;
                bool pages = (ioflag & IO_VMIO) != 0;

                SDT_PROBE2(fusefs, , vnops, trace, 1, "direct write of vnode");

                err = fuse_vnode_size(vp, &filesize, cred, curthread);
                if (err)
                        goto out;

                start = uio->uio_offset;
                end = start + uio->uio_resid;
                if (!pages) {
                        err = fuse_inval_buf_range(vp, filesize, start,
                            end);
                        if (err)
                                goto out;
                }
                err = fuse_write_directbackend(vp, uio, cred, fufh,
                        filesize, ioflag, pages);
        } else {
                SDT_PROBE2(fusefs, , vnops, trace, 1,
                        "buffered write of vnode");
                if (!fsess_opt_writeback(vnode_mount(vp)))
                        ioflag |= IO_SYNC;
                err = fuse_write_biobackend(vp, uio, cred, fufh, ioflag, pid);
        }
        fuse_internal_clear_suid_on_write(vp, cred, uio->uio_td);

out:
        if (closefufh)
                fuse_filehandle_close(vp, fufh, curthread, cred);

        return (err);
}

static daddr_t
fuse_gbp_getblkno(struct vnode *vp, vm_ooffset_t off)
{
        const int biosize = fuse_iosize(vp);

        return (off / biosize);
}

static int
fuse_gbp_getblksz(struct vnode *vp, daddr_t lbn, long *blksz)
{
        off_t filesize;
        int err;
        const int biosize = fuse_iosize(vp);

        err = fuse_vnode_size(vp, &filesize, NULL, NULL);
        if (err) {
                /* This will turn into a SIGBUS */
                return (EIO);
        } else if ((off_t)lbn * biosize >= filesize) {
                *blksz = 0;
        } else if ((off_t)(lbn + 1) * biosize > filesize) {
                *blksz = filesize - (off_t)lbn *biosize;
        } else {
                *blksz = biosize;
        }
        return (0);
}

/*
    struct vnop_getpages_args {
        struct vnode *a_vp;
        vm_page_t *a_m;
        int a_count;
        int a_reqpage;
    };
*/
static int
fuse_vnop_getpages(struct vop_getpages_args *ap)
{
        struct vnode *vp = ap->a_vp;

        if (!fsess_opt_mmap(vnode_mount(vp))) {
                SDT_PROBE2(fusefs, , vnops, trace, 1,
                        "called on non-cacheable vnode??\n");
                return (VM_PAGER_ERROR);
        }

        return (vfs_bio_getpages(vp, ap->a_m, ap->a_count, ap->a_rbehind,
            ap->a_rahead, fuse_gbp_getblkno, fuse_gbp_getblksz));
}

static const char extattr_namespace_separator = '.';

/*
    struct vop_getextattr_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
        int a_attrnamespace;
        const char *a_name;
        struct uio *a_uio;
        size_t *a_size;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_getextattr(struct vop_getextattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct fuse_dispatcher fdi;
        struct fuse_getxattr_in *get_xattr_in;
        struct fuse_getxattr_out *get_xattr_out;
        struct mount *mp = vnode_mount(vp);
        struct thread *td = ap->a_td;
        struct ucred *cred = ap->a_cred;
        char *prefix;
        char *attr_str;
        size_t len;
        int err;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        if (fsess_not_impl(mp, FUSE_GETXATTR))
                return (EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "extended attributes"));

        err = fuse_extattr_check_cred(vp, ap->a_attrnamespace, cred, td, VREAD);
        if (err)
                return err;

        /* Default to looking for user attributes. */
        if (ap->a_attrnamespace == EXTATTR_NAMESPACE_SYSTEM)
                prefix = EXTATTR_NAMESPACE_SYSTEM_STRING;
        else
                prefix = EXTATTR_NAMESPACE_USER_STRING;

        len = strlen(prefix) + sizeof(extattr_namespace_separator) +
            strlen(ap->a_name) + 1;

        fdisp_init(&fdi, len + sizeof(*get_xattr_in));
        fdisp_make_vp(&fdi, FUSE_GETXATTR, vp, td, cred);

        get_xattr_in = fdi.indata;
        /*
         * Check to see whether we're querying the available size or
         * issuing the actual request.  If we pass in 0, we get back struct
         * fuse_getxattr_out.  If we pass in a non-zero size, we get back
         * that much data, without the struct fuse_getxattr_out header.
         */
        if (uio == NULL)
                get_xattr_in->size = 0;
        else
                get_xattr_in->size = uio->uio_resid;

        attr_str = (char *)fdi.indata + sizeof(*get_xattr_in);
        snprintf(attr_str, len, "%s%c%s", prefix, extattr_namespace_separator,
            ap->a_name);

        err = fdisp_wait_answ(&fdi);
        if (err != 0) {
                if (err == ENOSYS) {
                        fsess_set_notimpl(mp, FUSE_GETXATTR);
                        err = (EXTERROR(EOPNOTSUPP, "This server does not "
                            "implement extended attributes"));
                }
                goto out;
        }

        get_xattr_out = fdi.answ;

        if (ap->a_size != NULL)
                *ap->a_size = get_xattr_out->size;

        if (uio != NULL)
                err = uiomove(fdi.answ, fdi.iosize, uio);

out:
        fdisp_destroy(&fdi);
        return (err);
}

/*
    struct vop_setextattr_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
        int a_attrnamespace;
        const char *a_name;
        struct uio *a_uio;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_setextattr(struct vop_setextattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct fuse_dispatcher fdi;
        struct fuse_setxattr_in *set_xattr_in;
        struct mount *mp = vnode_mount(vp);
        struct thread *td = ap->a_td;
        struct ucred *cred = ap->a_cred;
        size_t struct_size = FUSE_COMPAT_SETXATTR_IN_SIZE;
        char *prefix;
        size_t len;
        char *attr_str;
        int err;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        if (fsess_not_impl(mp, FUSE_SETXATTR))
                return (EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "setting extended attributes"));

        if (vfs_isrdonly(mp))
                return EROFS;

        /* Deleting xattrs must use VOP_DELETEEXTATTR instead */
        if (ap->a_uio == NULL) {
                /*
                 * If we got here as fallback from VOP_DELETEEXTATTR, then
                 * return EOPNOTSUPP.
                 */
                if (fsess_not_impl(mp, FUSE_REMOVEXATTR))
                        return (EXTERROR(EOPNOTSUPP, "This server does not "
                            "implement removing extended attributes"));
                else
                        return (EXTERROR(EINVAL, "DELETEEXTATTR should be used "
                            "to remove extattrs"));
        }

        err = fuse_extattr_check_cred(vp, ap->a_attrnamespace, cred, td,
                VWRITE);
        if (err)
                return err;

        /* Default to looking for user attributes. */
        if (ap->a_attrnamespace == EXTATTR_NAMESPACE_SYSTEM)
                prefix = EXTATTR_NAMESPACE_SYSTEM_STRING;
        else
                prefix = EXTATTR_NAMESPACE_USER_STRING;

        len = strlen(prefix) + sizeof(extattr_namespace_separator) +
            strlen(ap->a_name) + 1;

        /* older FUSE servers  use a smaller fuse_setxattr_in struct*/
        if (fuse_get_mpdata(mp)->dataflags & FSESS_SETXATTR_EXT)
                struct_size = sizeof(*set_xattr_in);

        fdisp_init(&fdi, len + struct_size + uio->uio_resid);
        fdisp_make_vp(&fdi, FUSE_SETXATTR, vp, td, cred);

        set_xattr_in = fdi.indata;
        set_xattr_in->size = uio->uio_resid;

        if (fuse_get_mpdata(mp)->dataflags & FSESS_SETXATTR_EXT) {
                set_xattr_in->setxattr_flags = 0;
                set_xattr_in->padding = 0;
        }

        attr_str = (char *)fdi.indata + struct_size;
        snprintf(attr_str, len, "%s%c%s", prefix, extattr_namespace_separator,
            ap->a_name);

        err = uiomove((char *)fdi.indata + struct_size + len,
            uio->uio_resid, uio);
        if (err != 0) {
                goto out;
        }

        err = fdisp_wait_answ(&fdi);

        if (err == ENOSYS) {
                fsess_set_notimpl(mp, FUSE_SETXATTR);
                err = EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "setting extended attributes");
        }
        if (err == ERESTART) {
                /* Can't restart after calling uiomove */
                err = EINTR;
        }

out:
        fdisp_destroy(&fdi);
        return (err);
}

/*
 * The Linux / FUSE extended attribute list is simply a collection of
 * NUL-terminated strings.  The FreeBSD extended attribute list is a single
 * byte length followed by a non-NUL terminated string.  So, this allows
 * conversion of the Linux / FUSE format to the FreeBSD format in place.
 * Linux attribute names are reported with the namespace as a prefix (e.g.
 * "user.attribute_name"), but in FreeBSD they are reported without the
 * namespace prefix (e.g. "attribute_name").  So, we're going from:
 *
 * user.attr_name1\0user.attr_name2\0
 *
 * to:
 *
 * <num>attr_name1<num>attr_name2
 *
 * Where "<num>" is a single byte number of characters in the attribute name.
 * 
 * Args:
 * prefix - exattr namespace prefix string
 * list, list_len - input list with namespace prefixes
 * bsd_list, bsd_list_len - output list compatible with bsd vfs
 */
static int
fuse_xattrlist_convert(char *prefix, const char *list, int list_len,
    char *bsd_list, int *bsd_list_len)
{
        int len, pos, dist_to_next, prefix_len;

        pos = 0;
        *bsd_list_len = 0;
        prefix_len = strlen(prefix);

        while (pos < list_len && list[pos] != '\0') {
                dist_to_next = strlen(&list[pos]) + 1;
                if (bcmp(&list[pos], prefix, prefix_len) == 0 &&
                    list[pos + prefix_len] == extattr_namespace_separator) {
                        len = dist_to_next -
                            (prefix_len + sizeof(extattr_namespace_separator)) - 1;
                        if (len >= EXTATTR_MAXNAMELEN)
                                return (ENAMETOOLONG);

                        bsd_list[*bsd_list_len] = len;
                        memcpy(&bsd_list[*bsd_list_len + 1],
                            &list[pos + prefix_len +
                            sizeof(extattr_namespace_separator)], len);

                        *bsd_list_len += len + 1;
                }

                pos += dist_to_next;
        }

        return (0);
}

/*
 * List extended attributes
 *
 * The FUSE_LISTXATTR operation is based on Linux's listxattr(2) syscall, which
 * has a number of differences compared to its FreeBSD equivalent,
 * extattr_list_file:
 *
 * - FUSE_LISTXATTR returns all extended attributes across all namespaces,
 *   whereas listxattr(2) only returns attributes for a single namespace
 * - FUSE_LISTXATTR prepends each attribute name with "namespace."
 * - If the provided buffer is not large enough to hold the result,
 *   FUSE_LISTXATTR should return ERANGE, whereas listxattr is expected to
 *   return as many results as will fit.
 */
/*
    struct vop_listextattr_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
        int a_attrnamespace;
        struct uio *a_uio;
        size_t *a_size;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_listextattr(struct vop_listextattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct fuse_dispatcher fdi;
        struct fuse_listxattr_in *list_xattr_in;
        struct fuse_listxattr_out *list_xattr_out;
        struct mount *mp = vnode_mount(vp);
        struct thread *td = ap->a_td;
        struct ucred *cred = ap->a_cred;
        char *prefix;
        char *bsd_list = NULL;
        char *linux_list;
        int bsd_list_len;
        int linux_list_len;
        int err;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        if (fsess_not_impl(mp, FUSE_LISTXATTR))
                return (EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "extended attributes"));

        err = fuse_extattr_check_cred(vp, ap->a_attrnamespace, cred, td, VREAD);
        if (err)
                return err;

        /*
         * Add space for a NUL and the period separator if enabled.
         * Default to looking for user attributes.
         */
        if (ap->a_attrnamespace == EXTATTR_NAMESPACE_SYSTEM)
                prefix = EXTATTR_NAMESPACE_SYSTEM_STRING;
        else
                prefix = EXTATTR_NAMESPACE_USER_STRING;

        fdisp_init(&fdi, sizeof(*list_xattr_in));
        fdisp_make_vp(&fdi, FUSE_LISTXATTR, vp, td, cred);

        /*
         * Retrieve Linux / FUSE compatible list size.
         */
        list_xattr_in = fdi.indata;
        list_xattr_in->size = 0;

        err = fdisp_wait_answ(&fdi);
        if (err != 0) {
                if (err == ENOSYS) {
                        fsess_set_notimpl(mp, FUSE_LISTXATTR);
                        err = EXTERROR(EOPNOTSUPP, "This server does not "
                            "implement extended attributes");
                }
                goto out;
        }

        list_xattr_out = fdi.answ;
        linux_list_len = list_xattr_out->size;
        if (linux_list_len == 0) {
                if (ap->a_size != NULL)
                        *ap->a_size = linux_list_len;
                goto out;
        }

        /*
         * Retrieve Linux / FUSE compatible list values.
         */
        fdisp_refresh_vp(&fdi, FUSE_LISTXATTR, vp, td, cred);
        list_xattr_in = fdi.indata;
        list_xattr_in->size = linux_list_len;

        err = fdisp_wait_answ(&fdi);
        if (err == ERANGE) {
                /* 
                 * Race detected.  The attribute list must've grown since the
                 * first FUSE_LISTXATTR call.  Start over.  Go all the way back
                 * to userland so we can process signals, if necessary, before
                 * restarting.
                 */
                err = ERESTART;
                goto out;
        } else if (err != 0)
                goto out;

        linux_list = fdi.answ;
        /* FUSE doesn't allow the server to return more data than requested */
        if (fdi.iosize > linux_list_len) {
                struct fuse_data *data = fuse_get_mpdata(mp);

                fuse_warn(data, FSESS_WARN_LSEXTATTR_LONG,
                        "server returned "
                        "more extended attribute data than requested; "
                        "should've returned ERANGE instead.");
        } else {
                /* But returning less data is fine */
                linux_list_len = fdi.iosize;
        }

        /*
         * Retrieve the BSD compatible list values.
         * The Linux / FUSE attribute list format isn't the same
         * as FreeBSD's format. So we need to transform it into
         * FreeBSD's format before giving it to the user.
         */
        bsd_list = malloc(linux_list_len, M_TEMP, M_WAITOK);
        err = fuse_xattrlist_convert(prefix, linux_list, linux_list_len,
            bsd_list, &bsd_list_len);
        if (err != 0)
                goto out;

        if (ap->a_size != NULL)
                *ap->a_size = bsd_list_len;

        if (uio != NULL)
                err = uiomove(bsd_list, bsd_list_len, uio);

out:
        free(bsd_list, M_TEMP);
        fdisp_destroy(&fdi);
        return (err);
}

/*
    struct vop_deallocate_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
        off_t *a_offset;
        off_t *a_len;
        int a_flags;
        int a_ioflag;
        struct ucred *a_cred;
    };
*/
static int
fuse_vnop_deallocate(struct vop_deallocate_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct mount *mp = vnode_mount(vp);
        struct fuse_filehandle *fufh;
        struct fuse_dispatcher fdi;
        struct fuse_fallocate_in *ffi;
        struct ucred *cred = ap->a_cred;
        pid_t pid = curthread->td_proc->p_pid;
        off_t *len = ap->a_len;
        off_t *offset = ap->a_offset;
        int ioflag = ap->a_ioflag;
        off_t filesize;
        int err;
        bool closefufh = false;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        if (vfs_isrdonly(mp))
                return (EROFS);

        if (fsess_not_impl(mp, FUSE_FALLOCATE))
                goto fallback;

        err = fuse_filehandle_getrw(vp, FWRITE, &fufh, cred, pid);
        if (err == EBADF && vnode_mount(vp)->mnt_flag & MNT_EXPORTED) {
                /*
                 * nfsd will do I/O without first doing VOP_OPEN.  We
                 * must implicitly open the file here
                 */
                err = fuse_filehandle_open(vp, FWRITE, &fufh, curthread, cred);
                closefufh = true;
        }
        if (err)
                return (err);

        fuse_vnode_update(vp, FN_MTIMECHANGE | FN_CTIMECHANGE);

        err = fuse_vnode_size(vp, &filesize, cred, curthread);
        if (err)
                goto out;
        fuse_inval_buf_range(vp, filesize, *offset, *offset + *len);

        fdisp_init(&fdi, sizeof(*ffi));
        fdisp_make_vp(&fdi, FUSE_FALLOCATE, vp, curthread, cred);
        ffi = fdi.indata;
        ffi->fh = fufh->fh_id;
        ffi->offset = *offset;
        ffi->length = *len;
        /*
         * FreeBSD's fspacectl is equivalent to Linux's fallocate with
         * mode == FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE
         */
        ffi->mode = FUSE_FALLOC_FL_PUNCH_HOLE | FUSE_FALLOC_FL_KEEP_SIZE;
        err = fdisp_wait_answ(&fdi);

        if (err == ENOSYS) {
                fdisp_destroy(&fdi);
                fsess_set_notimpl(mp, FUSE_FALLOCATE);
                goto fallback;
        } else if (err == EOPNOTSUPP) {
                /*
                 * The file system server does not support FUSE_FALLOCATE with
                 * the supplied mode for this particular file.
                 */
                fdisp_destroy(&fdi);
                goto fallback;
        } else if (!err) {
                /*
                 * Clip the returned offset to EoF.  Do it here rather than
                 * before FUSE_FALLOCATE just in case the kernel's cached file
                 * size is out of date.  Unfortunately, FUSE does not return
                 * any information about filesize from that operation.
                 */
                *offset = MIN(*offset + *len, filesize);
                *len = 0;
                fuse_vnode_undirty_cached_timestamps(vp, false);
                fuse_internal_clear_suid_on_write(vp, cred, curthread);

                if (ioflag & IO_SYNC)
                        err = fuse_internal_fsync(vp, curthread, MNT_WAIT,
                            false);
        }

        fdisp_destroy(&fdi);
out:
        if (closefufh)
                fuse_filehandle_close(vp, fufh, curthread, cred);

        return (err);

fallback:
        if (closefufh)
                fuse_filehandle_close(vp, fufh, curthread, cred);

        return (vop_stddeallocate(ap));
}

/*
   struct vop_delayed_setsize_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
  };
 */
static int
fuse_vnop_delayed_setsize(struct vop_delayed_setsize_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct fuse_vnode_data *fvdat = VTOFUD(ap->a_vp);
        bool shrink = (fvdat->flag & FN_DELAYED_TRUNCATE) != 0;
        int err;

        if (!fvdat)
                return (0);

        err = fuse_vnode_setsize_immediate(vp, shrink);
        fvdat->flag &= ~FN_DELAYED_TRUNCATE;

        return (err);
}

/*
    struct vop_deleteextattr_args {
        struct vop_generic_args a_gen;
        struct vnode *a_vp;
        int a_attrnamespace;
        const char *a_name;
        struct ucred *a_cred;
        struct thread *a_td;
    };
*/
static int
fuse_vnop_deleteextattr(struct vop_deleteextattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct fuse_dispatcher fdi;
        struct mount *mp = vnode_mount(vp);
        struct thread *td = ap->a_td;
        struct ucred *cred = ap->a_cred;
        char *prefix;
        size_t len;
        char *attr_str;
        int err;

        if (fuse_isdeadfs(vp))
                return (EXTERROR(ENXIO, "This FUSE session is about "
                    "to be closed"));

        if (fsess_not_impl(mp, FUSE_REMOVEXATTR))
                return (EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "removing extended attributes"));

        if (vfs_isrdonly(mp))
                return EROFS;

        err = fuse_extattr_check_cred(vp, ap->a_attrnamespace, cred, td,
                VWRITE);
        if (err)
                return err;

        /* Default to looking for user attributes. */
        if (ap->a_attrnamespace == EXTATTR_NAMESPACE_SYSTEM)
                prefix = EXTATTR_NAMESPACE_SYSTEM_STRING;
        else
                prefix = EXTATTR_NAMESPACE_USER_STRING;

        len = strlen(prefix) + sizeof(extattr_namespace_separator) +
            strlen(ap->a_name) + 1;

        fdisp_init(&fdi, len);
        fdisp_make_vp(&fdi, FUSE_REMOVEXATTR, vp, td, cred);

        attr_str = fdi.indata;
        snprintf(attr_str, len, "%s%c%s", prefix, extattr_namespace_separator,
            ap->a_name);

        err = fdisp_wait_answ(&fdi);
        if (err == ENOSYS) {
                fsess_set_notimpl(mp, FUSE_REMOVEXATTR);
                err = EXTERROR(EOPNOTSUPP, "This server does not implement "
                    "removing extended attributes");
        }

        fdisp_destroy(&fdi);
        return (err);
}

/*
    struct vnop_print_args {
        struct vnode *a_vp;
    };
*/
static int
fuse_vnop_print(struct vop_print_args *ap)
{
        struct fuse_vnode_data *fvdat = VTOFUD(ap->a_vp);

        printf("nodeid: %ju, parent nodeid: %ju, nlookup: %ju, flag: %#x\n",
            (uintmax_t)VTOILLU(ap->a_vp), (uintmax_t)fvdat->parent_nid,
            (uintmax_t)fvdat->nlookup,
            fvdat->flag);

        return 0;
}

/*
 * Get an NFS filehandle for a FUSE file.
 *
 * This will only work for FUSE file systems that guarantee the uniqueness of
 * nodeid:generation, which most don't.
 */
/*
vop_vptofh {
        IN struct vnode *a_vp;
        IN struct fid *a_fhp;
};
*/
static int
fuse_vnop_vptofh(struct vop_vptofh_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct fuse_vnode_data *fvdat = VTOFUD(vp);
        struct fuse_fid *fhp = (struct fuse_fid *)(ap->a_fhp);
        _Static_assert(sizeof(struct fuse_fid) <= sizeof(struct fid),
                "FUSE fid type is too big");
        struct mount *mp = vnode_mount(vp);
        struct fuse_data *data = fuse_get_mpdata(mp);
        struct vattr va;
        int err;

        if (!(data->dataflags & FSESS_EXPORT_SUPPORT)) {
                /* NFS requires lookups for "." and ".." */
                SDT_PROBE2(fusefs, , vnops, trace, 1,
                        "VOP_VPTOFH without FUSE_EXPORT_SUPPORT");
                return (EXTERROR(EOPNOTSUPP, "This server is "
                    "missing FUSE_EXPORT_SUPPORT"));
        }
        if ((mp->mnt_flag & MNT_EXPORTED) &&
                fsess_is_impl(mp, FUSE_OPENDIR))
        {
                /*
                 * NFS is stateless, so nfsd must reopen a directory on every
                 * call to VOP_READDIR, passing in the d_off field from the
                 * final dirent of the previous invocation.  But if the server
                 * implements FUSE_OPENDIR, the FUSE protocol does not
                 * guarantee that d_off will be valid after a directory is
                 * closed and reopened.  So prohibit exporting FUSE file
                 * systems that implement FUSE_OPENDIR.
                 *
                 * But userspace NFS servers don't have this problem.
                 */
                SDT_PROBE2(fusefs, , vnops, trace, 1,
                        "VOP_VPTOFH with FUSE_OPENDIR");
                return (EXTERROR(EOPNOTSUPP, "This server implements "
                    "FUSE_OPENDIR so is not compatible with getfh"));
        }

        err = fuse_internal_getattr(vp, &va, curthread->td_ucred, curthread);
        if (err)
                return err;

        /*ip = VTOI(ap->a_vp);*/
        /*ufhp = (struct ufid *)ap->a_fhp;*/
        fhp->len = sizeof(struct fuse_fid);
        fhp->nid = fvdat->nid;
        if (fvdat->generation <= UINT32_MAX)
                fhp->gen = fvdat->generation;
        else
                return (EXTERROR(EOVERFLOW, "inode generation "
                    "number overflow"));
        return (0);
}