/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1999-2004 Poul-Henning Kamp
 * Copyright (c) 1999 Michael Smith
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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.
 * 3. Neither the name of the University 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 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 THE 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/conf.h>
#include <sys/smp.h>
#include <sys/devctl.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/libkern.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/filedesc.h>
#include <sys/reboot.h>
#include <sys/sbuf.h>
#include <sys/stdarg.h>
#include <sys/syscallsubr.h>
#include <sys/sysproto.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/taskqueue.h>
#include <sys/vnode.h>
#include <vm/uma.h>

#include <geom/geom.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

#define VFS_MOUNTARG_SIZE_MAX   (1024 * 64)

static int      vfs_domount(struct thread *td, const char *fstype, char *fspath,
                    uint64_t fsflags, bool only_export, bool jail_export,
                    struct vfsoptlist **optlist);
static void     free_mntarg(struct mntarg *ma);

static int      usermount = 0;
SYSCTL_INT(_vfs, OID_AUTO, usermount, CTLFLAG_RW, &usermount, 0,
    "Unprivileged users may mount and unmount file systems");

static bool     default_autoro = false;
SYSCTL_BOOL(_vfs, OID_AUTO, default_autoro, CTLFLAG_RW, &default_autoro, 0,
    "Retry failed r/w mount as r/o if no explicit ro/rw option is specified");

static bool     recursive_forced_unmount = false;
SYSCTL_BOOL(_vfs, OID_AUTO, recursive_forced_unmount, CTLFLAG_RW,
    &recursive_forced_unmount, 0, "Recursively unmount stacked upper mounts"
    " when a file system is forcibly unmounted");

static SYSCTL_NODE(_vfs, OID_AUTO, deferred_unmount,
    CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "deferred unmount controls");

static unsigned int     deferred_unmount_retry_limit = 10;
SYSCTL_UINT(_vfs_deferred_unmount, OID_AUTO, retry_limit, CTLFLAG_RW,
    &deferred_unmount_retry_limit, 0,
    "Maximum number of retries for deferred unmount failure");

static int      deferred_unmount_retry_delay_hz;
SYSCTL_INT(_vfs_deferred_unmount, OID_AUTO, retry_delay_hz, CTLFLAG_RW,
    &deferred_unmount_retry_delay_hz, 0,
    "Delay in units of [1/kern.hz]s when retrying a failed deferred unmount");

static int      deferred_unmount_total_retries = 0;
SYSCTL_INT(_vfs_deferred_unmount, OID_AUTO, total_retries, CTLFLAG_RD,
    &deferred_unmount_total_retries, 0,
    "Total number of retried deferred unmounts");

MALLOC_DEFINE(M_MOUNT, "mount", "vfs mount structure");
MALLOC_DEFINE(M_STATFS, "statfs", "statfs structure");
static uma_zone_t mount_zone;

/* List of mounted filesystems. */
struct mntlist mountlist = TAILQ_HEAD_INITIALIZER(mountlist);

/* For any iteration/modification of mountlist */
struct mtx_padalign __exclusive_cache_line mountlist_mtx;

EVENTHANDLER_LIST_DEFINE(vfs_mounted);
EVENTHANDLER_LIST_DEFINE(vfs_unmounted);

static void vfs_deferred_unmount(void *arg, int pending);
static struct timeout_task deferred_unmount_task;
static struct mtx deferred_unmount_lock;
MTX_SYSINIT(deferred_unmount, &deferred_unmount_lock, "deferred_unmount",
    MTX_DEF);
static STAILQ_HEAD(, mount) deferred_unmount_list =
    STAILQ_HEAD_INITIALIZER(deferred_unmount_list);
TASKQUEUE_DEFINE_THREAD(deferred_unmount);

static void mount_devctl_event(const char *type, struct mount *mp, bool donew);

/*
 * Global opts, taken by all filesystems
 */
static const char *global_opts[] = {
        "errmsg",
        "fstype",
        "fspath",
        "ro",
        "rw",
        "nosuid",
        "noexec",
        NULL
};

static int
mount_init(void *mem, int size, int flags)
{
        struct mount *mp;

        mp = (struct mount *)mem;
        mtx_init(&mp->mnt_mtx, "struct mount mtx", NULL, MTX_DEF);
        mtx_init(&mp->mnt_listmtx, "struct mount vlist mtx", NULL, MTX_DEF);
        lockinit(&mp->mnt_explock, PVFS, "explock", 0, 0);
        lockinit(&mp->mnt_renamelock, PVFS, "rename", 0, 0);
        mp->mnt_pcpu = uma_zalloc_pcpu(pcpu_zone_16, M_WAITOK | M_ZERO);
        mp->mnt_ref = 0;
        mp->mnt_vfs_ops = 1;
        mp->mnt_rootvnode = NULL;
        return (0);
}

static void
mount_fini(void *mem, int size)
{
        struct mount *mp;

        mp = (struct mount *)mem;
        uma_zfree_pcpu(pcpu_zone_16, mp->mnt_pcpu);
        lockdestroy(&mp->mnt_renamelock);
        lockdestroy(&mp->mnt_explock);
        mtx_destroy(&mp->mnt_listmtx);
        mtx_destroy(&mp->mnt_mtx);
}

static void
vfs_mount_init(void *dummy __unused)
{
        TIMEOUT_TASK_INIT(taskqueue_deferred_unmount, &deferred_unmount_task,
            0, vfs_deferred_unmount, NULL);
        deferred_unmount_retry_delay_hz = hz;
        mount_zone = uma_zcreate("Mountpoints", sizeof(struct mount), NULL,
            NULL, mount_init, mount_fini, UMA_ALIGN_CACHE, UMA_ZONE_NOFREE);
        mtx_init(&mountlist_mtx, "mountlist", NULL, MTX_DEF);
}
SYSINIT(vfs_mount, SI_SUB_VFS, SI_ORDER_ANY, vfs_mount_init, NULL);

/*
 * ---------------------------------------------------------------------
 * Functions for building and sanitizing the mount options
 */

/* Remove one mount option. */
static void
vfs_freeopt(struct vfsoptlist *opts, struct vfsopt *opt)
{

        TAILQ_REMOVE(opts, opt, link);
        free(opt->name, M_MOUNT);
        if (opt->value != NULL)
                free(opt->value, M_MOUNT);
        free(opt, M_MOUNT);
}

/* Release all resources related to the mount options. */
void
vfs_freeopts(struct vfsoptlist *opts)
{
        struct vfsopt *opt;

        while (!TAILQ_EMPTY(opts)) {
                opt = TAILQ_FIRST(opts);
                vfs_freeopt(opts, opt);
        }
        free(opts, M_MOUNT);
}

void
vfs_deleteopt(struct vfsoptlist *opts, const char *name)
{
        struct vfsopt *opt, *temp;

        if (opts == NULL)
                return;
        TAILQ_FOREACH_SAFE(opt, opts, link, temp)  {
                if (strcmp(opt->name, name) == 0)
                        vfs_freeopt(opts, opt);
        }
}

static int
vfs_isopt_ro(const char *opt)
{

        if (strcmp(opt, "ro") == 0 || strcmp(opt, "rdonly") == 0 ||
            strcmp(opt, "norw") == 0)
                return (1);
        return (0);
}

static int
vfs_isopt_rw(const char *opt)
{

        if (strcmp(opt, "rw") == 0 || strcmp(opt, "noro") == 0)
                return (1);
        return (0);
}

/*
 * Check if options are equal (with or without the "no" prefix).
 */
static int
vfs_equalopts(const char *opt1, const char *opt2)
{
        char *p;

        /* "opt" vs. "opt" or "noopt" vs. "noopt" */
        if (strcmp(opt1, opt2) == 0)
                return (1);
        /* "noopt" vs. "opt" */
        if (strncmp(opt1, "no", 2) == 0 && strcmp(opt1 + 2, opt2) == 0)
                return (1);
        /* "opt" vs. "noopt" */
        if (strncmp(opt2, "no", 2) == 0 && strcmp(opt1, opt2 + 2) == 0)
                return (1);
        while ((p = strchr(opt1, '.')) != NULL &&
            !strncmp(opt1, opt2, ++p - opt1)) {
                opt2 += p - opt1;
                opt1 = p;
                /* "foo.noopt" vs. "foo.opt" */
                if (strncmp(opt1, "no", 2) == 0 && strcmp(opt1 + 2, opt2) == 0)
                        return (1);
                /* "foo.opt" vs. "foo.noopt" */
                if (strncmp(opt2, "no", 2) == 0 && strcmp(opt1, opt2 + 2) == 0)
                        return (1);
        }
        /* "ro" / "rdonly" / "norw" / "rw" / "noro" */
        if ((vfs_isopt_ro(opt1) || vfs_isopt_rw(opt1)) &&
            (vfs_isopt_ro(opt2) || vfs_isopt_rw(opt2)))
                return (1);
        return (0);
}

/*
 * If a mount option is specified several times,
 * (with or without the "no" prefix) only keep
 * the last occurrence of it.
 */
static void
vfs_sanitizeopts(struct vfsoptlist *opts)
{
        struct vfsopt *opt, *opt2, *tmp;

        TAILQ_FOREACH_REVERSE(opt, opts, vfsoptlist, link) {
                opt2 = TAILQ_PREV(opt, vfsoptlist, link);
                while (opt2 != NULL) {
                        if (vfs_equalopts(opt->name, opt2->name)) {
                                tmp = TAILQ_PREV(opt2, vfsoptlist, link);
                                vfs_freeopt(opts, opt2);
                                opt2 = tmp;
                        } else {
                                opt2 = TAILQ_PREV(opt2, vfsoptlist, link);
                        }
                }
        }
}

/*
 * Build a linked list of mount options from a struct uio.
 */
int
vfs_buildopts(struct uio *auio, struct vfsoptlist **options)
{
        struct vfsoptlist *opts;
        struct vfsopt *opt;
        size_t memused, namelen, optlen;
        unsigned int i, iovcnt;
        int error;

        opts = malloc(sizeof(struct vfsoptlist), M_MOUNT, M_WAITOK);
        TAILQ_INIT(opts);
        memused = 0;
        iovcnt = auio->uio_iovcnt;
        for (i = 0; i < iovcnt; i += 2) {
                namelen = auio->uio_iov[i].iov_len;
                optlen = auio->uio_iov[i + 1].iov_len;
                memused += sizeof(struct vfsopt) + optlen + namelen;
                /*
                 * Avoid consuming too much memory, and attempts to overflow
                 * memused.
                 */
                if (memused > VFS_MOUNTARG_SIZE_MAX ||
                    optlen > VFS_MOUNTARG_SIZE_MAX ||
                    namelen > VFS_MOUNTARG_SIZE_MAX) {
                        error = EINVAL;
                        goto bad;
                }

                opt = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK);
                opt->name = malloc(namelen, M_MOUNT, M_WAITOK);
                opt->value = NULL;
                opt->len = 0;
                opt->pos = i / 2;
                opt->seen = 0;

                /*
                 * Do this early, so jumps to "bad" will free the current
                 * option.
                 */
                TAILQ_INSERT_TAIL(opts, opt, link);

                if (auio->uio_segflg == UIO_SYSSPACE) {
                        bcopy(auio->uio_iov[i].iov_base, opt->name, namelen);
                } else {
                        error = copyin(auio->uio_iov[i].iov_base, opt->name,
                            namelen);
                        if (error)
                                goto bad;
                }
                /* Ensure names are null-terminated strings. */
                if (namelen == 0 || opt->name[namelen - 1] != '\0') {
                        error = EINVAL;
                        goto bad;
                }
                if (optlen != 0) {
                        opt->len = optlen;
                        opt->value = malloc(optlen, M_MOUNT, M_WAITOK);
                        if (auio->uio_segflg == UIO_SYSSPACE) {
                                bcopy(auio->uio_iov[i + 1].iov_base, opt->value,
                                    optlen);
                        } else {
                                error = copyin(auio->uio_iov[i + 1].iov_base,
                                    opt->value, optlen);
                                if (error)
                                        goto bad;
                        }
                }
        }
        vfs_sanitizeopts(opts);
        *options = opts;
        return (0);
bad:
        vfs_freeopts(opts);
        return (error);
}

/*
 * Merge the old mount options with the new ones passed
 * in the MNT_UPDATE case.
 *
 * XXX: This function will keep a "nofoo" option in the new
 * options.  E.g, if the option's canonical name is "foo",
 * "nofoo" ends up in the mount point's active options.
 */
static void
vfs_mergeopts(struct vfsoptlist *toopts, struct vfsoptlist *oldopts)
{
        struct vfsopt *opt, *new;

        TAILQ_FOREACH(opt, oldopts, link) {
                new = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK);
                new->name = strdup(opt->name, M_MOUNT);
                if (opt->len != 0) {
                        new->value = malloc(opt->len, M_MOUNT, M_WAITOK);
                        bcopy(opt->value, new->value, opt->len);
                } else
                        new->value = NULL;
                new->len = opt->len;
                new->seen = opt->seen;
                TAILQ_INSERT_HEAD(toopts, new, link);
        }
        vfs_sanitizeopts(toopts);
}

/*
 * Mount a filesystem.
 */
#ifndef _SYS_SYSPROTO_H_
struct nmount_args {
        struct iovec *iovp;
        unsigned int iovcnt;
        int flags;
};
#endif
int
sys_nmount(struct thread *td, struct nmount_args *uap)
{
        struct uio *auio;
        int error;
        u_int iovcnt;
        uint64_t flags;

        /*
         * Mount flags are now 64-bits. On 32-bit archtectures only
         * 32-bits are passed in, but from here on everything handles
         * 64-bit flags correctly.
         */
        flags = uap->flags;

        AUDIT_ARG_FFLAGS(flags);
        CTR4(KTR_VFS, "%s: iovp %p with iovcnt %d and flags %d", __func__,
            uap->iovp, uap->iovcnt, flags);

        /*
         * Filter out MNT_ROOTFS.  We do not want clients of nmount() in
         * userspace to set this flag, but we must filter it out if we want
         * MNT_UPDATE on the root file system to work.
         * MNT_ROOTFS should only be set by the kernel when mounting its
         * root file system.
         */
        flags &= ~MNT_ROOTFS;

        iovcnt = uap->iovcnt;
        /*
         * Check that we have an even number of iovec's
         * and that we have at least two options.
         */
        if ((iovcnt & 1) || (iovcnt < 4)) {
                CTR2(KTR_VFS, "%s: failed for invalid iovcnt %d", __func__,
                    uap->iovcnt);
                return (EINVAL);
        }

        error = copyinuio(uap->iovp, iovcnt, &auio);
        if (error) {
                CTR2(KTR_VFS, "%s: failed for invalid uio op with %d errno",
                    __func__, error);
                return (error);
        }
        error = vfs_donmount(td, flags, auio);

        freeuio(auio);
        return (error);
}

/*
 * ---------------------------------------------------------------------
 * Various utility functions
 */

/*
 * Get a reference on a mount point from a vnode.
 *
 * The vnode is allowed to be passed unlocked and race against dooming. Note in
 * such case there are no guarantees the referenced mount point will still be
 * associated with it after the function returns.
 */
struct mount *
vfs_ref_from_vp(struct vnode *vp)
{
        struct mount *mp;
        struct mount_pcpu *mpcpu;

        mp = atomic_load_ptr(&vp->v_mount);
        if (__predict_false(mp == NULL)) {
                return (mp);
        }
        if (vfs_op_thread_enter(mp, mpcpu)) {
                if (__predict_true(mp == vp->v_mount)) {
                        vfs_mp_count_add_pcpu(mpcpu, ref, 1);
                        vfs_op_thread_exit(mp, mpcpu);
                } else {
                        vfs_op_thread_exit(mp, mpcpu);
                        mp = NULL;
                }
        } else {
                MNT_ILOCK(mp);
                if (mp == vp->v_mount) {
                        MNT_REF(mp);
                        MNT_IUNLOCK(mp);
                } else {
                        MNT_IUNLOCK(mp);
                        mp = NULL;
                }
        }
        return (mp);
}

void
vfs_ref(struct mount *mp)
{
        struct mount_pcpu *mpcpu;

        CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
        if (vfs_op_thread_enter(mp, mpcpu)) {
                vfs_mp_count_add_pcpu(mpcpu, ref, 1);
                vfs_op_thread_exit(mp, mpcpu);
                return;
        }

        MNT_ILOCK(mp);
        MNT_REF(mp);
        MNT_IUNLOCK(mp);
}

/*
 * Register ump as an upper mount of the mount associated with
 * vnode vp.  This registration will be tracked through
 * mount_upper_node upper, which should be allocated by the
 * caller and stored in per-mount data associated with mp.
 *
 * If successful, this function will return the mount associated
 * with vp, and will ensure that it cannot be unmounted until
 * ump has been unregistered as one of its upper mounts.
 * 
 * Upon failure this function will return NULL.
 */
struct mount *
vfs_register_upper_from_vp(struct vnode *vp, struct mount *ump,
    struct mount_upper_node *upper)
{
        struct mount *mp;

        mp = atomic_load_ptr(&vp->v_mount);
        if (mp == NULL)
                return (NULL);
        MNT_ILOCK(mp);
        if (mp != vp->v_mount ||
            ((mp->mnt_kern_flag & (MNTK_UNMOUNT | MNTK_RECURSE)) != 0)) {
                MNT_IUNLOCK(mp);
                return (NULL);
        }
        KASSERT(ump != mp, ("upper and lower mounts are identical"));
        upper->mp = ump;
        MNT_REF(mp);
        TAILQ_INSERT_TAIL(&mp->mnt_uppers, upper, mnt_upper_link);
        MNT_IUNLOCK(mp);
        return (mp);
}

/*
 * Register upper mount ump to receive vnode unlink/reclaim
 * notifications from lower mount mp. This registration will
 * be tracked through mount_upper_node upper, which should be
 * allocated by the caller and stored in per-mount data
 * associated with mp.
 *
 * ump must already be registered as an upper mount of mp
 * through a call to vfs_register_upper_from_vp().
 */
void
vfs_register_for_notification(struct mount *mp, struct mount *ump,
    struct mount_upper_node *upper)
{
        upper->mp = ump;
        MNT_ILOCK(mp);
        TAILQ_INSERT_TAIL(&mp->mnt_notify, upper, mnt_upper_link);
        MNT_IUNLOCK(mp);
}

static void
vfs_drain_upper_locked(struct mount *mp)
{
        mtx_assert(MNT_MTX(mp), MA_OWNED);
        while (mp->mnt_upper_pending != 0) {
                mp->mnt_kern_flag |= MNTK_UPPER_WAITER;
                msleep(&mp->mnt_uppers, MNT_MTX(mp), 0, "mntupw", 0);
        }
}

/*
 * Undo a previous call to vfs_register_for_notification().
 * The mount represented by upper must be currently registered
 * as an upper mount for mp.
 */
void
vfs_unregister_for_notification(struct mount *mp,
    struct mount_upper_node *upper)
{
        MNT_ILOCK(mp);
        vfs_drain_upper_locked(mp);
        TAILQ_REMOVE(&mp->mnt_notify, upper, mnt_upper_link);
        MNT_IUNLOCK(mp);
}

/*
 * Undo a previous call to vfs_register_upper_from_vp().
 * This must be done before mp can be unmounted.
 */
void
vfs_unregister_upper(struct mount *mp, struct mount_upper_node *upper)
{
        MNT_ILOCK(mp);
        KASSERT((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0,
            ("registered upper with pending unmount"));
        vfs_drain_upper_locked(mp);
        TAILQ_REMOVE(&mp->mnt_uppers, upper, mnt_upper_link);
        if ((mp->mnt_kern_flag & MNTK_TASKQUEUE_WAITER) != 0 &&
            TAILQ_EMPTY(&mp->mnt_uppers)) {
                mp->mnt_kern_flag &= ~MNTK_TASKQUEUE_WAITER;
                wakeup(&mp->mnt_taskqueue_link);
        }
        MNT_REL(mp);
        MNT_IUNLOCK(mp);
}

void
vfs_rel(struct mount *mp)
{
        struct mount_pcpu *mpcpu;

        CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
        if (vfs_op_thread_enter(mp, mpcpu)) {
                vfs_mp_count_sub_pcpu(mpcpu, ref, 1);
                vfs_op_thread_exit(mp, mpcpu);
                return;
        }

        MNT_ILOCK(mp);
        MNT_REL(mp);
        MNT_IUNLOCK(mp);
}

/*
 * Allocate and initialize the mount point struct.
 */
struct mount *
vfs_mount_alloc(struct vnode *vp, struct vfsconf *vfsp, const char *fspath,
    struct ucred *cred)
{
        struct mount *mp;

        mp = uma_zalloc(mount_zone, M_WAITOK);
        bzero(&mp->mnt_startzero,
            __rangeof(struct mount, mnt_startzero, mnt_endzero));
        mp->mnt_kern_flag = 0;
        mp->mnt_flag = 0;
        mp->mnt_rootvnode = NULL;
        mp->mnt_vnodecovered = NULL;
        mp->mnt_op = NULL;
        mp->mnt_vfc = NULL;
        TAILQ_INIT(&mp->mnt_nvnodelist);
        mp->mnt_nvnodelistsize = 0;
        TAILQ_INIT(&mp->mnt_lazyvnodelist);
        mp->mnt_lazyvnodelistsize = 0;
        MPPASS(mp->mnt_ref == 0 && mp->mnt_lockref == 0 &&
            mp->mnt_writeopcount == 0, mp);
        MPASSERT(mp->mnt_vfs_ops == 1, mp,
            ("vfs_ops should be 1 but %d found", mp->mnt_vfs_ops));
        (void) vfs_busy(mp, MBF_NOWAIT);
        mp->mnt_op = vfsp->vfc_vfsops;
        mp->mnt_vfc = vfsp;
        mp->mnt_stat.f_type = vfsp->vfc_typenum;
        mp->mnt_gen++;
        strlcpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
        mp->mnt_vnodecovered = vp;
        mp->mnt_cred = crdup(cred);
        mp->mnt_stat.f_owner = cred->cr_uid;
        strlcpy(mp->mnt_stat.f_mntonname, fspath, MNAMELEN);
        mp->mnt_iosize_max = DFLTPHYS;
#ifdef MAC
        mac_mount_init(mp);
        mac_mount_create(cred, mp);
#endif
        arc4rand(&mp->mnt_hashseed, sizeof mp->mnt_hashseed, 0);
        mp->mnt_upper_pending = 0;
        TAILQ_INIT(&mp->mnt_uppers);
        TAILQ_INIT(&mp->mnt_notify);
        mp->mnt_taskqueue_flags = 0;
        mp->mnt_unmount_retries = 0;
        return (mp);
}

/*
 * Destroy the mount struct previously allocated by vfs_mount_alloc().
 */
void
vfs_mount_destroy(struct mount *mp)
{

        MPPASS(mp->mnt_vfs_ops != 0, mp);

        vfs_assert_mount_counters(mp);

        MNT_ILOCK(mp);
        mp->mnt_kern_flag |= MNTK_REFEXPIRE;
        if (mp->mnt_kern_flag & MNTK_MWAIT) {
                mp->mnt_kern_flag &= ~MNTK_MWAIT;
                wakeup(mp);
        }
        while (mp->mnt_ref)
                msleep(mp, MNT_MTX(mp), PVFS, "mntref", 0);
        KASSERT(mp->mnt_ref == 0,
            ("%s: invalid refcount in the drain path @ %s:%d", __func__,
            __FILE__, __LINE__));
        MPPASS(mp->mnt_writeopcount == 0, mp);
        MPPASS(mp->mnt_secondary_writes == 0, mp);
        if (!TAILQ_EMPTY(&mp->mnt_nvnodelist)) {
                struct vnode *vp;

                TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes)
                        vn_printf(vp, "dangling vnode ");
                panic("unmount: dangling vnode");
        }
        KASSERT(mp->mnt_upper_pending == 0, ("mnt_upper_pending"));
        KASSERT(TAILQ_EMPTY(&mp->mnt_uppers), ("mnt_uppers"));
        KASSERT(TAILQ_EMPTY(&mp->mnt_notify), ("mnt_notify"));
        MPPASS(mp->mnt_nvnodelistsize == 0, mp);
        MPPASS(mp->mnt_lazyvnodelistsize == 0, mp);
        MPPASS(mp->mnt_lockref == 0, mp);
        MNT_IUNLOCK(mp);

        MPASSERT(mp->mnt_vfs_ops == 1, mp,
            ("vfs_ops should be 1 but %d found", mp->mnt_vfs_ops));

        MPASSERT(mp->mnt_rootvnode == NULL, mp,
            ("mount point still has a root vnode %p", mp->mnt_rootvnode));

        if (mp->mnt_vnodecovered != NULL)
                vrele(mp->mnt_vnodecovered);
#ifdef MAC
        mac_mount_destroy(mp);
#endif
        if (mp->mnt_opt != NULL)
                vfs_freeopts(mp->mnt_opt);
        if (mp->mnt_exjail != NULL) {
                atomic_subtract_int(&mp->mnt_exjail->cr_prison->pr_exportcnt,
                    1);
                crfree(mp->mnt_exjail);
        }
        if (mp->mnt_export != NULL) {
                vfs_free_addrlist(mp->mnt_export);
                free(mp->mnt_export, M_MOUNT);
        }
        vfsconf_lock();
        mp->mnt_vfc->vfc_refcount--;
        vfsconf_unlock();
        crfree(mp->mnt_cred);
        uma_zfree(mount_zone, mp);
}

static bool
vfs_should_downgrade_to_ro_mount(uint64_t fsflags, int error)
{
        /* This is an upgrade of an exisiting mount. */
        if ((fsflags & MNT_UPDATE) != 0)
                return (false);
        /* This is already an R/O mount. */
        if ((fsflags & MNT_RDONLY) != 0)
                return (false);

        switch (error) {
        case ENODEV:    /* generic, geom, ... */
        case EACCES:    /* cam/scsi, ... */
        case EROFS:     /* md, mmcsd, ... */
                /*
                 * These errors can be returned by the storage layer to signal
                 * that the media is read-only.  No harm in the R/O mount
                 * attempt if the error was returned for some other reason.
                 */
                return (true);
        default:
                return (false);
        }
}

int
vfs_donmount(struct thread *td, uint64_t fsflags, struct uio *fsoptions)
{
        struct vfsoptlist *optlist;
        struct vfsopt *opt, *tmp_opt;
        char *fstype, *fspath, *errmsg;
        int error, fstypelen, fspathlen, errmsg_len, errmsg_pos;
        bool autoro, has_nonexport, only_export, jail_export;

        errmsg = fspath = NULL;
        errmsg_len = fspathlen = 0;
        errmsg_pos = -1;
        autoro = default_autoro;

        error = vfs_buildopts(fsoptions, &optlist);
        if (error)
                return (error);

        if (vfs_getopt(optlist, "errmsg", (void **)&errmsg, &errmsg_len) == 0)
                errmsg_pos = vfs_getopt_pos(optlist, "errmsg");

        /*
         * We need these two options before the others,
         * and they are mandatory for any filesystem.
         * Ensure they are NUL terminated as well.
         */
        fstypelen = 0;
        error = vfs_getopt(optlist, "fstype", (void **)&fstype, &fstypelen);
        if (error || fstypelen <= 0 || fstype[fstypelen - 1] != '\0') {
                error = EINVAL;
                if (errmsg != NULL)
                        strncpy(errmsg, "Invalid fstype", errmsg_len);
                goto bail;
        }
        fspathlen = 0;
        error = vfs_getopt(optlist, "fspath", (void **)&fspath, &fspathlen);
        if (error || fspathlen <= 0 || fspath[fspathlen - 1] != '\0') {
                error = EINVAL;
                if (errmsg != NULL)
                        strncpy(errmsg, "Invalid fspath", errmsg_len);
                goto bail;
        }

        /*
         * Check to see that "export" is only used with the "update", "fstype",
         * "fspath", "from" and "errmsg" options when in a vnet jail.
         * These are the ones used to set/update exports by mountd(8).
         * If only the above options are set in a jail that can run mountd(8),
         * then the jail_export argument of vfs_domount() will be true.
         * When jail_export is true, the vfs_suser() check does not cause
         * failure, but limits the update to exports only.
         * This allows mountd(8) running within the vnet jail
         * to export file systems visible within the jail, but
         * mounted outside of the jail.
         */
        /*
         * We need to see if we have the "update" option
         * before we call vfs_domount(), since vfs_domount() has special
         * logic based on MNT_UPDATE.  This is very important
         * when we want to update the root filesystem.
         */
        has_nonexport = false;
        only_export = false;
        TAILQ_FOREACH_SAFE(opt, optlist, link, tmp_opt) {
                int do_freeopt = 0;

                if (strcmp(opt->name, "export") != 0 &&
                    strcmp(opt->name, "update") != 0 &&
                    strcmp(opt->name, "fstype") != 0 &&
                    strcmp(opt->name, "fspath") != 0 &&
                    strcmp(opt->name, "from") != 0 &&
                    strcmp(opt->name, "errmsg") != 0)
                        has_nonexport = true;
                if (strcmp(opt->name, "update") == 0) {
                        fsflags |= MNT_UPDATE;
                        do_freeopt = 1;
                }
                else if (strcmp(opt->name, "async") == 0)
                        fsflags |= MNT_ASYNC;
                else if (strcmp(opt->name, "force") == 0) {
                        fsflags |= MNT_FORCE;
                        do_freeopt = 1;
                }
                else if (strcmp(opt->name, "reload") == 0) {
                        fsflags |= MNT_RELOAD;
                        do_freeopt = 1;
                }
                else if (strcmp(opt->name, "multilabel") == 0)
                        fsflags |= MNT_MULTILABEL;
                else if (strcmp(opt->name, "noasync") == 0)
                        fsflags &= ~MNT_ASYNC;
                else if (strcmp(opt->name, "noatime") == 0)
                        fsflags |= MNT_NOATIME;
                else if (strcmp(opt->name, "atime") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonoatime", M_MOUNT);
                }
                else if (strcmp(opt->name, "noclusterr") == 0)
                        fsflags |= MNT_NOCLUSTERR;
                else if (strcmp(opt->name, "clusterr") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonoclusterr", M_MOUNT);
                }
                else if (strcmp(opt->name, "noclusterw") == 0)
                        fsflags |= MNT_NOCLUSTERW;
                else if (strcmp(opt->name, "clusterw") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonoclusterw", M_MOUNT);
                }
                else if (strcmp(opt->name, "noexec") == 0)
                        fsflags |= MNT_NOEXEC;
                else if (strcmp(opt->name, "exec") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonoexec", M_MOUNT);
                }
                else if (strcmp(opt->name, "nosuid") == 0)
                        fsflags |= MNT_NOSUID;
                else if (strcmp(opt->name, "suid") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonosuid", M_MOUNT);
                }
                else if (strcmp(opt->name, "nosymfollow") == 0)
                        fsflags |= MNT_NOSYMFOLLOW;
                else if (strcmp(opt->name, "symfollow") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("nonosymfollow", M_MOUNT);
                }
                else if (strcmp(opt->name, "noro") == 0) {
                        fsflags &= ~MNT_RDONLY;
                        autoro = false;
                }
                else if (strcmp(opt->name, "rw") == 0) {
                        fsflags &= ~MNT_RDONLY;
                        autoro = false;
                }
                else if (strcmp(opt->name, "ro") == 0) {
                        fsflags |= MNT_RDONLY;
                        autoro = false;
                }
                else if (strcmp(opt->name, "rdonly") == 0) {
                        free(opt->name, M_MOUNT);
                        opt->name = strdup("ro", M_MOUNT);
                        fsflags |= MNT_RDONLY;
                        autoro = false;
                }
                else if (strcmp(opt->name, "autoro") == 0) {
                        do_freeopt = 1;
                        autoro = true;
                }
                else if (strcmp(opt->name, "suiddir") == 0)
                        fsflags |= MNT_SUIDDIR;
                else if (strcmp(opt->name, "sync") == 0)
                        fsflags |= MNT_SYNCHRONOUS;
                else if (strcmp(opt->name, "union") == 0)
                        fsflags |= MNT_UNION;
                else if (strcmp(opt->name, "export") == 0) {
                        fsflags |= MNT_EXPORTED;
                        only_export = true;
                } else if (strcmp(opt->name, "automounted") == 0) {
                        fsflags |= MNT_AUTOMOUNTED;
                        do_freeopt = 1;
                } else if (strcmp(opt->name, "nocover") == 0) {
                        fsflags |= MNT_NOCOVER;
                        do_freeopt = 1;
                } else if (strcmp(opt->name, "cover") == 0) {
                        fsflags &= ~MNT_NOCOVER;
                        do_freeopt = 1;
                } else if (strcmp(opt->name, "emptydir") == 0) {
                        fsflags |= MNT_EMPTYDIR;
                        do_freeopt = 1;
                } else if (strcmp(opt->name, "noemptydir") == 0) {
                        fsflags &= ~MNT_EMPTYDIR;
                        do_freeopt = 1;
                }
                if (do_freeopt)
                        vfs_freeopt(optlist, opt);
        }

        /*
         * Be ultra-paranoid about making sure the type and fspath
         * variables will fit in our mp buffers, including the
         * terminating NUL.
         */
        if (fstypelen > MFSNAMELEN || fspathlen > MNAMELEN) {
                error = ENAMETOOLONG;
                goto bail;
        }

        /*
         * only_export is set to true only if exports are being
         * updated and nothing else is being updated.
         */
        if (has_nonexport)
                only_export = false;
        /*
         * If only_export is true and the caller is running within a
         * vnet prison that can run mountd(8), set jail_export true.
         */
        jail_export = false;
        if (only_export && jailed(td->td_ucred) &&
            prison_check_nfsd(td->td_ucred))
                jail_export = true;

        error = vfs_domount(td, fstype, fspath, fsflags, only_export,
            jail_export, &optlist);
        if (error == ENODEV) {
                error = EINVAL;
                if (errmsg != NULL)
                        strncpy(errmsg, "Invalid fstype", errmsg_len);
                goto bail;
        }

        /*
         * See if we can mount in the read-only mode if the error code suggests
         * that it could be possible and the mount options allow for that.
         * Never try it if "[no]{ro|rw}" has been explicitly requested and not
         * overridden by "autoro".
         */
        if (autoro && vfs_should_downgrade_to_ro_mount(fsflags, error)) {
                printf("%s: R/W mount failed, possibly R/O media,"
                    " trying R/O mount\n", __func__);
                fsflags |= MNT_RDONLY;
                error = vfs_domount(td, fstype, fspath, fsflags, only_export,
                    jail_export, &optlist);
        }
bail:
        /* copyout the errmsg */
        if (errmsg_pos != -1 && ((2 * errmsg_pos + 1) < fsoptions->uio_iovcnt)
            && errmsg_len > 0 && errmsg != NULL) {
                if (fsoptions->uio_segflg == UIO_SYSSPACE) {
                        bcopy(errmsg,
                            fsoptions->uio_iov[2 * errmsg_pos + 1].iov_base,
                            fsoptions->uio_iov[2 * errmsg_pos + 1].iov_len);
                } else {
                        (void)copyout(errmsg,
                            fsoptions->uio_iov[2 * errmsg_pos + 1].iov_base,
                            fsoptions->uio_iov[2 * errmsg_pos + 1].iov_len);
                }
        }

        if (optlist != NULL)
                vfs_freeopts(optlist);
        return (error);
}

/*
 * Old mount API.
 */
#ifndef _SYS_SYSPROTO_H_
struct mount_args {
        char    *type;
        char    *path;
        int     flags;
        caddr_t data;
};
#endif
/* ARGSUSED */
int
sys_mount(struct thread *td, struct mount_args *uap)
{
        char *fstype;
        struct vfsconf *vfsp = NULL;
        struct mntarg *ma = NULL;
        uint64_t flags;
        int error;

        /*
         * Mount flags are now 64-bits. On 32-bit architectures only
         * 32-bits are passed in, but from here on everything handles
         * 64-bit flags correctly.
         */
        flags = uap->flags;

        AUDIT_ARG_FFLAGS(flags);

        /*
         * Filter out MNT_ROOTFS.  We do not want clients of mount() in
         * userspace to set this flag, but we must filter it out if we want
         * MNT_UPDATE on the root file system to work.
         * MNT_ROOTFS should only be set by the kernel when mounting its
         * root file system.
         */
        flags &= ~MNT_ROOTFS;

        fstype = malloc(MFSNAMELEN, M_TEMP, M_WAITOK);
        error = copyinstr(uap->type, fstype, MFSNAMELEN, NULL);
        if (error) {
                free(fstype, M_TEMP);
                return (error);
        }

        AUDIT_ARG_TEXT(fstype);
        vfsp = vfs_byname_kld(fstype, td, &error);
        free(fstype, M_TEMP);
        if (vfsp == NULL)
                return (EINVAL);
        if (((vfsp->vfc_flags & VFCF_SBDRY) != 0 &&
            vfsp->vfc_vfsops_sd->vfs_cmount == NULL) ||
            ((vfsp->vfc_flags & VFCF_SBDRY) == 0 &&
            vfsp->vfc_vfsops->vfs_cmount == NULL))
                return (EOPNOTSUPP);

        ma = mount_argsu(ma, "fstype", uap->type, MFSNAMELEN);
        ma = mount_argsu(ma, "fspath", uap->path, MNAMELEN);
        ma = mount_argb(ma, flags & MNT_RDONLY, "noro");
        ma = mount_argb(ma, !(flags & MNT_NOSUID), "nosuid");
        ma = mount_argb(ma, !(flags & MNT_NOEXEC), "noexec");

        if ((vfsp->vfc_flags & VFCF_SBDRY) != 0)
                return (vfsp->vfc_vfsops_sd->vfs_cmount(ma, uap->data, flags));
        return (vfsp->vfc_vfsops->vfs_cmount(ma, uap->data, flags));
}

/*
 * vfs_domount_first(): first file system mount (not update)
 */
static int
vfs_domount_first(
        struct thread *td,              /* Calling thread. */
        struct vfsconf *vfsp,           /* File system type. */
        char *fspath,                   /* Mount path. */
        struct vnode *vp,               /* Vnode to be covered. */
        uint64_t fsflags,               /* Flags common to all filesystems. */
        struct vfsoptlist **optlist     /* Options local to the filesystem. */
        )
{
        struct vattr va;
        struct mount *mp;
        struct vnode *newdp, *rootvp;
        int error, error1;
        bool unmounted;

        ASSERT_VOP_ELOCKED(vp, __func__);
        KASSERT((fsflags & MNT_UPDATE) == 0, ("MNT_UPDATE shouldn't be here"));

        /*
         * If the jail of the calling thread lacks permission for this type of
         * file system, or is trying to cover its own root, deny immediately.
         */
        if (jailed(td->td_ucred) && (!prison_allow(td->td_ucred,
            vfsp->vfc_prison_flag) || vp == td->td_ucred->cr_prison->pr_root)) {
                vput(vp);
                vfs_unref_vfsconf(vfsp);
                return (EPERM);
        }

        /*
         * If the user is not root, ensure that they own the directory
         * onto which we are attempting to mount.
         */
        error = VOP_GETATTR(vp, &va, td->td_ucred);
        if (error == 0 && va.va_uid != td->td_ucred->cr_uid)
                error = priv_check_cred(td->td_ucred, PRIV_VFS_ADMIN);
        if (error == 0)
                error = vinvalbuf(vp, V_SAVE, 0, 0);
        if (vfsp->vfc_flags & VFCF_FILEMOUNT) {
                if (error == 0 && vp->v_type != VDIR && vp->v_type != VREG)
                        error = EINVAL;
                /*
                 * For file mounts, ensure that there is only one hardlink to the file.
                 */
                if (error == 0 && vp->v_type == VREG && va.va_nlink != 1)
                        error = EINVAL;
        } else {
                if (error == 0 && vp->v_type != VDIR)
                        error = ENOTDIR;
        }
        if (error == 0 && (fsflags & MNT_EMPTYDIR) != 0)
                error = vn_dir_check_empty(vp);
        if (error == 0) {
                VI_LOCK(vp);
                if ((vp->v_iflag & VI_MOUNT) == 0 && vp->v_mountedhere == NULL)
                        vp->v_iflag |= VI_MOUNT;
                else
                        error = EBUSY;
                VI_UNLOCK(vp);
        }
        if (error != 0) {
                vput(vp);
                vfs_unref_vfsconf(vfsp);
                return (error);
        }
        vn_seqc_write_begin(vp);
        VOP_UNLOCK(vp);

        /* Allocate and initialize the filesystem. */
        mp = vfs_mount_alloc(vp, vfsp, fspath, td->td_ucred);
        /* XXXMAC: pass to vfs_mount_alloc? */
        mp->mnt_optnew = *optlist;
        /* Set the mount level flags. */
        mp->mnt_flag = (fsflags &
            (MNT_UPDATEMASK | MNT_ROOTFS | MNT_RDONLY | MNT_FORCE));

        /*
         * Mount the filesystem.
         * XXX The final recipients of VFS_MOUNT just overwrite the ndp they
         * get.  No freeing of cn_pnbuf.
         */
        error1 = 0;
        unmounted = true;
        if ((error = VFS_MOUNT(mp)) != 0 ||
            (error1 = VFS_STATFS(mp, &mp->mnt_stat)) != 0 ||
            (error1 = VFS_ROOT(mp, LK_EXCLUSIVE, &newdp)) != 0) {
                rootvp = NULL;
                if (error1 != 0) {
                        MPASS(error == 0);
                        rootvp = vfs_cache_root_clear(mp);
                        if (rootvp != NULL) {
                                vhold(rootvp);
                                vrele(rootvp);
                        }
                        (void)vn_start_write(NULL, &mp, V_WAIT);
                        MNT_ILOCK(mp);
                        mp->mnt_kern_flag |= MNTK_UNMOUNT | MNTK_UNMOUNTF;
                        MNT_IUNLOCK(mp);
                        VFS_PURGE(mp);
                        error = VFS_UNMOUNT(mp, 0);
                        vn_finished_write(mp);
                        if (error != 0) {
                                printf(
                    "failed post-mount (%d): rollback unmount returned %d\n",
                                    error1, error);
                                unmounted = false;
                        }
                        error = error1;
                }
                vfs_unbusy(mp);
                mp->mnt_vnodecovered = NULL;
                if (unmounted) {
                        /* XXXKIB wait for mnt_lockref drain? */
                        vfs_mount_destroy(mp);
                }
                VI_LOCK(vp);
                vp->v_iflag &= ~VI_MOUNT;
                VI_UNLOCK(vp);
                if (rootvp != NULL) {
                        vn_seqc_write_end(rootvp);
                        vdrop(rootvp);
                }
                vn_seqc_write_end(vp);
                vrele(vp);
                return (error);
        }
        vn_seqc_write_begin(newdp);
        VOP_UNLOCK(newdp);

        if (mp->mnt_opt != NULL)
                vfs_freeopts(mp->mnt_opt);
        mp->mnt_opt = mp->mnt_optnew;
        *optlist = NULL;

        /*
         * Prevent external consumers of mount options from reading mnt_optnew.
         */
        mp->mnt_optnew = NULL;

        MNT_ILOCK(mp);
        if ((mp->mnt_flag & MNT_ASYNC) != 0 &&
            (mp->mnt_kern_flag & MNTK_NOASYNC) == 0)
                mp->mnt_kern_flag |= MNTK_ASYNC;
        else
                mp->mnt_kern_flag &= ~MNTK_ASYNC;
        MNT_IUNLOCK(mp);

        /*
         * VIRF_MOUNTPOINT and v_mountedhere need to be set under the
         * vp lock to satisfy vfs_lookup() requirements.
         */
        VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY);
        VI_LOCK(vp);
        vn_irflag_set_locked(vp, VIRF_MOUNTPOINT);
        vp->v_mountedhere = mp;
        VI_UNLOCK(vp);
        VOP_UNLOCK(vp);
        cache_purge(vp);

        /*
         * We need to lock both vnodes.
         *
         * Use vn_lock_pair to avoid establishing an ordering between vnodes
         * from different filesystems.
         */
        vn_lock_pair(vp, false, LK_EXCLUSIVE, newdp, false, LK_EXCLUSIVE);

        VI_LOCK(vp);
        vp->v_iflag &= ~VI_MOUNT;
        VI_UNLOCK(vp);
        /* Place the new filesystem at the end of the mount list. */
        mtx_lock(&mountlist_mtx);
        TAILQ_INSERT_TAIL(&mountlist, mp, mnt_list);
        mtx_unlock(&mountlist_mtx);
        vfs_event_signal(NULL, VQ_MOUNT, 0);
        VOP_UNLOCK(vp);
        EVENTHANDLER_DIRECT_INVOKE(vfs_mounted, mp, newdp, td);
        VOP_UNLOCK(newdp);
        mount_devctl_event("MOUNT", mp, false);
        mountcheckdirs(vp, newdp);
        vn_seqc_write_end(vp);
        vn_seqc_write_end(newdp);
        vrele(newdp);
        if ((mp->mnt_flag & MNT_RDONLY) == 0)
                vfs_allocate_syncvnode(mp);
        vfs_op_exit(mp);
        vfs_unbusy(mp);
        return (0);
}

/*
 * vfs_domount_update(): update of mounted file system
 */
static int
vfs_domount_update(
        struct thread *td,              /* Calling thread. */
        struct vnode *vp,               /* Mount point vnode. */
        uint64_t fsflags,               /* Flags common to all filesystems. */
        bool only_export,               /* Got export option. */
        bool jail_export,               /* Got export option in vnet prison. */
        struct vfsoptlist **optlist     /* Options local to the filesystem. */
        )
{
        struct export_args export;
        struct o2export_args o2export;
        struct vnode *rootvp;
        void *bufp;
        struct mount *mp;
        int error, export_error, i, len, fsid_up_len;
        uint64_t flag, mnt_union;
        gid_t *grps;
        fsid_t *fsid_up;
        bool vfs_suser_failed;

        ASSERT_VOP_ELOCKED(vp, __func__);
        KASSERT((fsflags & MNT_UPDATE) != 0, ("MNT_UPDATE should be here"));
        mp = vp->v_mount;

        if ((vp->v_vflag & VV_ROOT) == 0) {
                if (vfs_copyopt(*optlist, "export", &export, sizeof(export))
                    == 0)
                        error = EXDEV;
                else
                        error = EINVAL;
                vput(vp);
                return (error);
        }

        /*
         * We only allow the filesystem to be reloaded if it
         * is currently mounted read-only.
         */
        flag = mp->mnt_flag;
        if ((fsflags & MNT_RELOAD) != 0 && (flag & MNT_RDONLY) == 0) {
                vput(vp);
                return (EOPNOTSUPP);    /* Needs translation */
        }
        /*
         * Only privileged root, or (if MNT_USER is set) the user that
         * did the original mount is permitted to update it.
         */
        /*
         * For the case of mountd(8) doing exports in a jail, the vfs_suser()
         * call does not cause failure.  vfs_domount() has already checked
         * that "root" is doing this and vfs_suser() will fail when
         * the file system has been mounted outside the jail.
         * jail_export set true indicates that "export" is not mixed
         * with other options that change mount behaviour.
         */
        vfs_suser_failed = false;
        error = vfs_suser(mp, td);
        if (jail_export && error != 0) {
                error = 0;
                vfs_suser_failed = true;
        }
        if (error != 0) {
                vput(vp);
                return (error);
        }
        if (vfs_busy(mp, MBF_NOWAIT)) {
                vput(vp);
                return (EBUSY);
        }
        VI_LOCK(vp);
        if ((vp->v_iflag & VI_MOUNT) != 0 || vp->v_mountedhere != NULL) {
                VI_UNLOCK(vp);
                vfs_unbusy(mp);
                vput(vp);
                return (EBUSY);
        }
        vp->v_iflag |= VI_MOUNT;
        VI_UNLOCK(vp);
        VOP_UNLOCK(vp);

        rootvp = NULL;
        vfs_op_enter(mp);
        vn_seqc_write_begin(vp);

        if (vfs_getopt(*optlist, "fsid", (void **)&fsid_up,
            &fsid_up_len) == 0) {
                if (fsid_up_len != sizeof(*fsid_up)) {
                        error = EINVAL;
                        goto end;
                }
                if (fsidcmp(fsid_up, &mp->mnt_stat.f_fsid) != 0) {
                        error = ENOENT;
                        goto end;
                }
                vfs_deleteopt(*optlist, "fsid");
        }

        mnt_union = 0;
        MNT_ILOCK(mp);
        if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0) {
                MNT_IUNLOCK(mp);
                error = EBUSY;
                goto end;
        }
        if (vfs_suser_failed) {
                KASSERT((fsflags & (MNT_EXPORTED | MNT_UPDATE)) ==
                    (MNT_EXPORTED | MNT_UPDATE),
                    ("%s: jailed export did not set expected fsflags",
                     __func__));
                /*
                 * For this case, only MNT_UPDATE and
                 * MNT_EXPORTED have been set in fsflags
                 * by the options.  Only set MNT_UPDATE,
                 * since that is the one that would be set
                 * when set in fsflags, below.
                 */
                mp->mnt_flag |= MNT_UPDATE;
        } else {
                mp->mnt_flag &= ~MNT_UPDATEMASK;
                if ((mp->mnt_flag & MNT_UNION) == 0 &&
                    (fsflags & MNT_UNION) != 0) {
                        fsflags &= ~MNT_UNION;
                        mnt_union = MNT_UNION;
                }
                mp->mnt_flag |= fsflags & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE |
                    MNT_SNAPSHOT | MNT_ROOTFS | MNT_UPDATEMASK | MNT_RDONLY);
                if ((mp->mnt_flag & MNT_ASYNC) == 0)
                        mp->mnt_kern_flag &= ~MNTK_ASYNC;
        }
        rootvp = vfs_cache_root_clear(mp);
        MNT_IUNLOCK(mp);
        mp->mnt_optnew = *optlist;
        vfs_mergeopts(mp->mnt_optnew, mp->mnt_opt);

        /*
         * Mount the filesystem.
         * XXX The final recipients of VFS_MOUNT just overwrite the ndp they
         * get.  No freeing of cn_pnbuf.
         */
        /*
         * When only updating mount exports, VFS_MOUNT() does not need to
         * be called, as indicated by only_export being set true.
         * For the case of mountd(8) doing exports from within a vnet jail,
         * "from" is typically not set correctly such that VFS_MOUNT() will
         * return ENOENT. For ZFS, there is a locking bug which can result in
         * deadlock if VFS_MOUNT() is called when extended attributes are
         * being updated.
         */
        error = 0;
        if (!only_export)
                error = VFS_MOUNT(mp);

        export_error = 0;
        /* Process the export option. */
        if (error == 0 && vfs_getopt(mp->mnt_optnew, "export", &bufp,
            &len) == 0) {
                /* Assume that there is only 1 ABI for each length. */
                switch (len) {
                case (sizeof(struct oexport_args)):
                        bzero(&o2export, sizeof(o2export));
                        /* FALLTHROUGH */
                case (sizeof(o2export)):
                        bcopy(bufp, &o2export, len);
                        export.ex_flags = (uint64_t)o2export.ex_flags;
                        export.ex_root = o2export.ex_root;
                        export.ex_uid = o2export.ex_anon.cr_uid;
                        export.ex_groups = NULL;
                        export.ex_ngroups = o2export.ex_anon.cr_ngroups;
                        if (export.ex_ngroups > 0) {
                                if (export.ex_ngroups <= XU_NGROUPS) {
                                        export.ex_groups = malloc(
                                            export.ex_ngroups * sizeof(gid_t),
                                            M_TEMP, M_WAITOK);
                                        for (i = 0; i < export.ex_ngroups; i++)
                                                export.ex_groups[i] =
                                                  o2export.ex_anon.cr_groups[i];
                                } else
                                        export_error = EINVAL;
                        } else if (export.ex_ngroups < 0)
                                export_error = EINVAL;
                        export.ex_addr = o2export.ex_addr;
                        export.ex_addrlen = o2export.ex_addrlen;
                        export.ex_mask = o2export.ex_mask;
                        export.ex_masklen = o2export.ex_masklen;
                        export.ex_indexfile = o2export.ex_indexfile;
                        export.ex_numsecflavors = o2export.ex_numsecflavors;
                        if (export.ex_numsecflavors < MAXSECFLAVORS) {
                                for (i = 0; i < export.ex_numsecflavors; i++)
                                        export.ex_secflavors[i] =
                                            o2export.ex_secflavors[i];
                        } else
                                export_error = EINVAL;
                        if (export_error == 0)
                                export_error = vfs_export(mp, &export, true);
                        free(export.ex_groups, M_TEMP);
                        break;
                case (sizeof(export)):
                        bcopy(bufp, &export, len);
                        grps = NULL;
                        if (export.ex_ngroups > 0) {
                                if (export.ex_ngroups <= ngroups_max + 1) {
                                        grps = malloc(export.ex_ngroups *
                                            sizeof(gid_t), M_TEMP, M_WAITOK);
                                        export_error = copyin(export.ex_groups,
                                            grps, export.ex_ngroups *
                                            sizeof(gid_t));
                                        if (export_error == 0)
                                                export.ex_groups = grps;
                                } else
                                        export_error = EINVAL;
                        } else if (export.ex_ngroups == 0)
                                export.ex_groups = NULL;
                        else
                                export_error = EINVAL;
                        if (export_error == 0)
                                export_error = vfs_export(mp, &export, true);
                        free(grps, M_TEMP);
                        break;
                default:
                        export_error = EINVAL;
                        break;
                }
        }

        MNT_ILOCK(mp);
        if (error == 0) {
                mp->mnt_flag &= ~(MNT_UPDATE | MNT_RELOAD | MNT_FORCE |
                    MNT_SNAPSHOT);
                mp->mnt_flag |= mnt_union;
        } else {
                /*
                 * If we fail, restore old mount flags. MNT_QUOTA is special,
                 * because it is not part of MNT_UPDATEMASK, but it could have
                 * changed in the meantime if quotactl(2) was called.
                 * All in all we want current value of MNT_QUOTA, not the old
                 * one.
                 */
                mp->mnt_flag = (mp->mnt_flag & MNT_QUOTA) | (flag & ~MNT_QUOTA);
        }
        if ((mp->mnt_flag & MNT_ASYNC) != 0 &&
            (mp->mnt_kern_flag & MNTK_NOASYNC) == 0)
                mp->mnt_kern_flag |= MNTK_ASYNC;
        else
                mp->mnt_kern_flag &= ~MNTK_ASYNC;
        MNT_IUNLOCK(mp);

        if (error != 0)
                goto end;

        mount_devctl_event("REMOUNT", mp, true);
        if (mp->mnt_opt != NULL)
                vfs_freeopts(mp->mnt_opt);
        mp->mnt_opt = mp->mnt_optnew;
        *optlist = NULL;
        (void)VFS_STATFS(mp, &mp->mnt_stat);
        /*
         * Prevent external consumers of mount options from reading
         * mnt_optnew.
         */
        mp->mnt_optnew = NULL;

        if ((mp->mnt_flag & MNT_RDONLY) == 0)
                vfs_allocate_syncvnode(mp);
        else
                vfs_deallocate_syncvnode(mp);
end:
        vfs_op_exit(mp);
        if (rootvp != NULL) {
                vn_seqc_write_end(rootvp);
                vrele(rootvp);
        }
        vn_seqc_write_end(vp);
        vfs_unbusy(mp);
        VI_LOCK(vp);
        vp->v_iflag &= ~VI_MOUNT;
        VI_UNLOCK(vp);
        vrele(vp);
        return (error != 0 ? error : export_error);
}

/*
 * vfs_domount(): actually attempt a filesystem mount.
 */
static int
vfs_domount(
        struct thread *td,              /* Calling thread. */
        const char *fstype,             /* Filesystem type. */
        char *fspath,                   /* Mount path. */
        uint64_t fsflags,               /* Flags common to all filesystems. */
        bool only_export,               /* Got export option. */
        bool jail_export,               /* Got export option in vnet prison. */
        struct vfsoptlist **optlist     /* Options local to the filesystem. */
        )
{
        struct vfsconf *vfsp;
        struct nameidata nd;
        struct vnode *vp;
        char *pathbuf;
        int error;

        /*
         * Be ultra-paranoid about making sure the type and fspath
         * variables will fit in our mp buffers, including the
         * terminating NUL.
         */
        if (strlen(fstype) >= MFSNAMELEN || strlen(fspath) >= MNAMELEN)
                return (ENAMETOOLONG);

        if (jail_export) {
                error = priv_check(td, PRIV_NFS_DAEMON);
                if (error)
                        return (error);
        } else if (jailed(td->td_ucred) || usermount == 0) {
                if ((error = priv_check(td, PRIV_VFS_MOUNT)) != 0)
                        return (error);
        }

        /*
         * Do not allow NFS export or MNT_SUIDDIR by unprivileged users.
         */
        if (fsflags & MNT_EXPORTED) {
                error = priv_check(td, PRIV_VFS_MOUNT_EXPORTED);
                if (error)
                        return (error);
        }
        if (fsflags & MNT_SUIDDIR) {
                error = priv_check(td, PRIV_VFS_MOUNT_SUIDDIR);
                if (error)
                        return (error);
        }
        /*
         * Silently enforce MNT_NOSUID and MNT_USER for unprivileged users.
         */
        if ((fsflags & (MNT_NOSUID | MNT_USER)) != (MNT_NOSUID | MNT_USER)) {
                if (priv_check(td, PRIV_VFS_MOUNT_NONUSER) != 0)
                        fsflags |= MNT_NOSUID | MNT_USER;
        }

        /* Load KLDs before we lock the covered vnode to avoid reversals. */
        vfsp = NULL;
        if ((fsflags & MNT_UPDATE) == 0) {
                /* Don't try to load KLDs if we're mounting the root. */
                if (fsflags & MNT_ROOTFS) {
                        if ((vfsp = vfs_byname(fstype)) == NULL)
                                return (ENODEV);
                } else {
                        if ((vfsp = vfs_byname_kld(fstype, td, &error)) == NULL)
                                return (error);
                }
        }

        /*
         * Get vnode to be covered or mount point's vnode in case of MNT_UPDATE.
         */
        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1 | WANTPARENT,
            UIO_SYSSPACE, fspath);
        error = namei(&nd);
        if (error != 0)
                return (error);
        vp = nd.ni_vp;
        /*
         * Don't allow stacking file mounts to work around problems with the way
         * that namei sets nd.ni_dvp to vp_crossmp for these.
         */
        if (vp->v_type == VREG)
                fsflags |= MNT_NOCOVER;
        if ((fsflags & MNT_UPDATE) == 0) {
                if ((vp->v_vflag & VV_ROOT) != 0 &&
                    (fsflags & MNT_NOCOVER) != 0) {
                        vput(vp);
                        error = EBUSY;
                        goto out;
                }
                pathbuf = malloc(MNAMELEN, M_TEMP, M_WAITOK);
                strcpy(pathbuf, fspath);
                /*
                 * Note: we allow any vnode type here. If the path sanity check
                 * succeeds, the type will be validated in vfs_domount_first
                 * above.
                 */
                if (vp->v_type == VDIR)
                        error = vn_path_to_global_path(td, vp, pathbuf,
                            MNAMELEN);
                else
                        error = vn_path_to_global_path_hardlink(td, vp,
                            nd.ni_dvp, pathbuf, MNAMELEN,
                            nd.ni_cnd.cn_nameptr, nd.ni_cnd.cn_namelen);
                if (error == 0) {
                        error = vfs_domount_first(td, vfsp, pathbuf, vp,
                            fsflags, optlist);
                }
                free(pathbuf, M_TEMP);
        } else
                error = vfs_domount_update(td, vp, fsflags, only_export,
                    jail_export, optlist);

out:
        NDFREE_PNBUF(&nd);
        vrele(nd.ni_dvp);

        return (error);
}

/*
 * Unmount a filesystem.
 *
 * Note: unmount takes a path to the vnode mounted on as argument, not
 * special file (as before).
 */
#ifndef _SYS_SYSPROTO_H_
struct unmount_args {
        char    *path;
        int     flags;
};
#endif
/* ARGSUSED */
int
sys_unmount(struct thread *td, struct unmount_args *uap)
{

        return (kern_unmount(td, uap->path, (unsigned)uap->flags));
}

int
kern_unmount(struct thread *td, const char *path, uint64_t flags)
{
        struct nameidata nd;
        struct mount *mp;
        char *fsidbuf, *pathbuf;
        fsid_t fsid;
        int error;

        AUDIT_ARG_VALUE(flags);
        if ((flags & (MNT_DEFERRED | MNT_RECURSE)) != 0)
                return (EINVAL);
        if (jailed(td->td_ucred) || usermount == 0) {
                error = priv_check(td, PRIV_VFS_UNMOUNT);
                if (error)
                        return (error);
        }

        if (flags & MNT_BYFSID) {
                fsidbuf = malloc(MNAMELEN, M_TEMP, M_WAITOK);
                error = copyinstr(path, fsidbuf, MNAMELEN, NULL);
                if (error) {
                        free(fsidbuf, M_TEMP);
                        return (error);
                }

                AUDIT_ARG_TEXT(fsidbuf);
                /* Decode the filesystem ID. */
                if (sscanf(fsidbuf, "FSID:%d:%d", &fsid.val[0], &fsid.val[1]) != 2) {
                        free(fsidbuf, M_TEMP);
                        return (EINVAL);
                }

                mp = vfs_getvfs(&fsid);
                free(fsidbuf, M_TEMP);
                if (mp == NULL) {
                        return (ENOENT);
                }
        } else {
                pathbuf = malloc(MNAMELEN, M_TEMP, M_WAITOK);
                error = copyinstr(path, pathbuf, MNAMELEN, NULL);
                if (error) {
                        free(pathbuf, M_TEMP);
                        return (error);
                }

                /*
                 * Try to find global path for path argument.
                 */
                NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
                    UIO_SYSSPACE, pathbuf);
                if (namei(&nd) == 0) {
                        NDFREE_PNBUF(&nd);
                        error = vn_path_to_global_path(td, nd.ni_vp, pathbuf,
                            MNAMELEN);
                        if (error == 0)
                                vput(nd.ni_vp);
                }
                mtx_lock(&mountlist_mtx);
                TAILQ_FOREACH_REVERSE(mp, &mountlist, mntlist, mnt_list) {
                        if (strcmp(mp->mnt_stat.f_mntonname, pathbuf) == 0) {
                                vfs_ref(mp);
                                break;
                        }
                }
                mtx_unlock(&mountlist_mtx);
                free(pathbuf, M_TEMP);
                if (mp == NULL) {
                        /*
                         * Previously we returned ENOENT for a nonexistent path and
                         * EINVAL for a non-mountpoint.  We cannot tell these apart
                         * now, so in the !MNT_BYFSID case return the more likely
                         * EINVAL for compatibility.
                         */
                        return (EINVAL);
                }
        }

        /*
         * Don't allow unmounting the root filesystem.
         */
        if (mp->mnt_flag & MNT_ROOTFS) {
                vfs_rel(mp);
                return (EINVAL);
        }
        error = dounmount(mp, flags, td);
        return (error);
}

/*
 * Return error if any of the vnodes, ignoring the root vnode
 * and the syncer vnode, have non-zero usecount.
 *
 * This function is purely advisory - it can return false positives
 * and negatives.
 */
static int
vfs_check_usecounts(struct mount *mp)
{
        struct vnode *vp, *mvp;

        MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
                if ((vp->v_vflag & VV_ROOT) == 0 && vp->v_type != VNON &&
                    vp->v_usecount != 0) {
                        VI_UNLOCK(vp);
                        MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
                        return (EBUSY);
                }
                VI_UNLOCK(vp);
        }

        return (0);
}

static void
dounmount_cleanup(struct mount *mp, struct vnode *coveredvp, int mntkflags)
{

        mtx_assert(MNT_MTX(mp), MA_OWNED);
        mp->mnt_kern_flag &= ~mntkflags;
        if ((mp->mnt_kern_flag & MNTK_MWAIT) != 0) {
                mp->mnt_kern_flag &= ~MNTK_MWAIT;
                wakeup(mp);
        }
        vfs_op_exit_locked(mp);
        MNT_IUNLOCK(mp);
        if (coveredvp != NULL) {
                VOP_UNLOCK(coveredvp);
                vdrop(coveredvp);
        }
        vn_finished_write(mp);
        vfs_rel(mp);
}

/*
 * There are various reference counters associated with the mount point.
 * Normally it is permitted to modify them without taking the mnt ilock,
 * but this behavior can be temporarily disabled if stable value is needed
 * or callers are expected to block (e.g. to not allow new users during
 * forced unmount).
 */
void
vfs_op_enter(struct mount *mp)
{
        struct mount_pcpu *mpcpu;
        int cpu;

        MNT_ILOCK(mp);
        mp->mnt_vfs_ops++;
        if (mp->mnt_vfs_ops > 1) {
                MNT_IUNLOCK(mp);
                return;
        }
        vfs_op_barrier_wait(mp);
        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);

                mp->mnt_ref += mpcpu->mntp_ref;
                mpcpu->mntp_ref = 0;

                mp->mnt_lockref += mpcpu->mntp_lockref;
                mpcpu->mntp_lockref = 0;

                mp->mnt_writeopcount += mpcpu->mntp_writeopcount;
                mpcpu->mntp_writeopcount = 0;
        }
        MPASSERT(mp->mnt_ref > 0 && mp->mnt_lockref >= 0 &&
            mp->mnt_writeopcount >= 0, mp,
            ("invalid count(s): ref %d lockref %d writeopcount %d",
            mp->mnt_ref, mp->mnt_lockref, mp->mnt_writeopcount));
        MNT_IUNLOCK(mp);
        vfs_assert_mount_counters(mp);
}

void
vfs_op_exit_locked(struct mount *mp)
{

        mtx_assert(MNT_MTX(mp), MA_OWNED);

        MPASSERT(mp->mnt_vfs_ops > 0, mp,
            ("invalid vfs_ops count %d", mp->mnt_vfs_ops));
        MPASSERT(mp->mnt_vfs_ops > 1 ||
            (mp->mnt_kern_flag & (MNTK_UNMOUNT | MNTK_SUSPEND)) == 0, mp,
            ("vfs_ops too low %d in unmount or suspend", mp->mnt_vfs_ops));
        mp->mnt_vfs_ops--;
}

void
vfs_op_exit(struct mount *mp)
{

        MNT_ILOCK(mp);
        vfs_op_exit_locked(mp);
        MNT_IUNLOCK(mp);
}

struct vfs_op_barrier_ipi {
        struct mount *mp;
        struct smp_rendezvous_cpus_retry_arg srcra;
};

static void
vfs_op_action_func(void *arg)
{
        struct vfs_op_barrier_ipi *vfsopipi;
        struct mount *mp;

        vfsopipi = __containerof(arg, struct vfs_op_barrier_ipi, srcra);
        mp = vfsopipi->mp;

        if (!vfs_op_thread_entered(mp))
                smp_rendezvous_cpus_done(arg);
}

static void
vfs_op_wait_func(void *arg, int cpu)
{
        struct vfs_op_barrier_ipi *vfsopipi;
        struct mount *mp;
        struct mount_pcpu *mpcpu;

        vfsopipi = __containerof(arg, struct vfs_op_barrier_ipi, srcra);
        mp = vfsopipi->mp;

        mpcpu = vfs_mount_pcpu_remote(mp, cpu);
        while (atomic_load_int(&mpcpu->mntp_thread_in_ops))
                cpu_spinwait();
}

void
vfs_op_barrier_wait(struct mount *mp)
{
        struct vfs_op_barrier_ipi vfsopipi;

        vfsopipi.mp = mp;

        smp_rendezvous_cpus_retry(all_cpus,
            smp_no_rendezvous_barrier,
            vfs_op_action_func,
            smp_no_rendezvous_barrier,
            vfs_op_wait_func,
            &vfsopipi.srcra);
}

#ifdef DIAGNOSTIC
void
vfs_assert_mount_counters(struct mount *mp)
{
        struct mount_pcpu *mpcpu;
        int cpu;

        if (mp->mnt_vfs_ops == 0)
                return;

        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);
                if (mpcpu->mntp_ref != 0 ||
                    mpcpu->mntp_lockref != 0 ||
                    mpcpu->mntp_writeopcount != 0)
                        vfs_dump_mount_counters(mp);
        }
}

void
vfs_dump_mount_counters(struct mount *mp)
{
        struct mount_pcpu *mpcpu;
        int ref, lockref, writeopcount;
        int cpu;

        printf("%s: mp %p vfs_ops %d\n", __func__, mp, mp->mnt_vfs_ops);

        printf("        ref : ");
        ref = mp->mnt_ref;
        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);
                printf("%d ", mpcpu->mntp_ref);
                ref += mpcpu->mntp_ref;
        }
        printf("\n");
        printf("    lockref : ");
        lockref = mp->mnt_lockref;
        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);
                printf("%d ", mpcpu->mntp_lockref);
                lockref += mpcpu->mntp_lockref;
        }
        printf("\n");
        printf("writeopcount: ");
        writeopcount = mp->mnt_writeopcount;
        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);
                printf("%d ", mpcpu->mntp_writeopcount);
                writeopcount += mpcpu->mntp_writeopcount;
        }
        printf("\n");

        printf("counter       struct total\n");
        printf("ref             %-5d  %-5d\n", mp->mnt_ref, ref);
        printf("lockref         %-5d  %-5d\n", mp->mnt_lockref, lockref);
        printf("writeopcount    %-5d  %-5d\n", mp->mnt_writeopcount, writeopcount);

        panic("invalid counts on struct mount");
}
#endif

int
vfs_mount_fetch_counter(struct mount *mp, enum mount_counter which)
{
        struct mount_pcpu *mpcpu;
        int cpu, sum;

        switch (which) {
        case MNT_COUNT_REF:
                sum = mp->mnt_ref;
                break;
        case MNT_COUNT_LOCKREF:
                sum = mp->mnt_lockref;
                break;
        case MNT_COUNT_WRITEOPCOUNT:
                sum = mp->mnt_writeopcount;
                break;
        }

        CPU_FOREACH(cpu) {
                mpcpu = vfs_mount_pcpu_remote(mp, cpu);
                switch (which) {
                case MNT_COUNT_REF:
                        sum += mpcpu->mntp_ref;
                        break;
                case MNT_COUNT_LOCKREF:
                        sum += mpcpu->mntp_lockref;
                        break;
                case MNT_COUNT_WRITEOPCOUNT:
                        sum += mpcpu->mntp_writeopcount;
                        break;
                }
        }
        return (sum);
}

static bool
deferred_unmount_enqueue(struct mount *mp, uint64_t flags, bool requeue,
    int timeout_ticks)
{
        bool enqueued;

        enqueued = false;
        mtx_lock(&deferred_unmount_lock);
        if ((mp->mnt_taskqueue_flags & MNT_DEFERRED) == 0 || requeue) {
                mp->mnt_taskqueue_flags = flags | MNT_DEFERRED;
                STAILQ_INSERT_TAIL(&deferred_unmount_list, mp,
                    mnt_taskqueue_link);
                enqueued = true;
        }
        mtx_unlock(&deferred_unmount_lock);

        if (enqueued) {
                taskqueue_enqueue_timeout(taskqueue_deferred_unmount,
                    &deferred_unmount_task, timeout_ticks);
        }

        return (enqueued);
}

/*
 * Taskqueue handler for processing async/recursive unmounts
 */
static void
vfs_deferred_unmount(void *argi __unused, int pending __unused)
{
        STAILQ_HEAD(, mount) local_unmounts;
        uint64_t flags;
        struct mount *mp, *tmp;
        int error;
        unsigned int retries;
        bool unmounted;

        STAILQ_INIT(&local_unmounts);
        mtx_lock(&deferred_unmount_lock);
        STAILQ_CONCAT(&local_unmounts, &deferred_unmount_list); 
        mtx_unlock(&deferred_unmount_lock);

        STAILQ_FOREACH_SAFE(mp, &local_unmounts, mnt_taskqueue_link, tmp) {
                flags = mp->mnt_taskqueue_flags;
                KASSERT((flags & MNT_DEFERRED) != 0,
                    ("taskqueue unmount without MNT_DEFERRED"));
                error = dounmount(mp, flags, curthread);
                if (error != 0) {
                        MNT_ILOCK(mp);
                        unmounted = ((mp->mnt_kern_flag & MNTK_REFEXPIRE) != 0);
                        MNT_IUNLOCK(mp);

                        /*
                         * The deferred unmount thread is the only thread that
                         * modifies the retry counts, so locking/atomics aren't
                         * needed here.
                         */
                        retries = (mp->mnt_unmount_retries)++;
                        deferred_unmount_total_retries++;
                        if (!unmounted && retries < deferred_unmount_retry_limit) {
                                deferred_unmount_enqueue(mp, flags, true,
                                    -deferred_unmount_retry_delay_hz);
                        } else {
                                if (retries >= deferred_unmount_retry_limit) {
                                        printf("giving up on deferred unmount "
                                            "of %s after %d retries, error %d\n",
                                            mp->mnt_stat.f_mntonname, retries, error);
                                }
                                vfs_rel(mp);
                        }
                }
        }
}

/*
 * Do the actual filesystem unmount.
 */
int
dounmount(struct mount *mp, uint64_t flags, struct thread *td)
{
        struct mount_upper_node *upper;
        struct vnode *coveredvp, *rootvp;
        int error;
        uint64_t async_flag;
        int mnt_gen_r;
        unsigned int retries;

        KASSERT((flags & MNT_DEFERRED) == 0 ||
            (flags & (MNT_RECURSE | MNT_FORCE)) == (MNT_RECURSE | MNT_FORCE),
            ("MNT_DEFERRED requires MNT_RECURSE | MNT_FORCE"));

        /*
         * If the caller has explicitly requested the unmount to be handled by
         * the taskqueue and we're not already in taskqueue context, queue
         * up the unmount request and exit.  This is done prior to any
         * credential checks; MNT_DEFERRED should be used only for kernel-
         * initiated unmounts and will therefore be processed with the
         * (kernel) credentials of the taskqueue thread.  Still, callers
         * should be sure this is the behavior they want.
         */
        if ((flags & MNT_DEFERRED) != 0 &&
            taskqueue_member(taskqueue_deferred_unmount, curthread) == 0) {
                if (!deferred_unmount_enqueue(mp, flags, false, 0))
                        vfs_rel(mp);
                return (EINPROGRESS);
        }

        /*
         * Only privileged root, or (if MNT_USER is set) the user that did the
         * original mount is permitted to unmount this filesystem.
         * This check should be made prior to queueing up any recursive
         * unmounts of upper filesystems.  Those unmounts will be executed
         * with kernel thread credentials and are expected to succeed, so
         * we must at least ensure the originating context has sufficient
         * privilege to unmount the base filesystem before proceeding with
         * the uppers.
         */
        error = vfs_suser(mp, td);
        if (error != 0) {
                KASSERT((flags & MNT_DEFERRED) == 0,
                    ("taskqueue unmount with insufficient privilege"));
                vfs_rel(mp);
                return (error);
        }

        if (recursive_forced_unmount && ((flags & MNT_FORCE) != 0))
                flags |= MNT_RECURSE;

        if ((flags & MNT_RECURSE) != 0) {
                KASSERT((flags & MNT_FORCE) != 0,
                    ("MNT_RECURSE requires MNT_FORCE"));

                MNT_ILOCK(mp);
                /*
                 * Set MNTK_RECURSE to prevent new upper mounts from being
                 * added, and note that an operation on the uppers list is in
                 * progress.  This will ensure that unregistration from the
                 * uppers list, and therefore any pending unmount of the upper
                 * FS, can't complete until after we finish walking the list.
                 */
                mp->mnt_kern_flag |= MNTK_RECURSE;
                mp->mnt_upper_pending++;
                TAILQ_FOREACH(upper, &mp->mnt_uppers, mnt_upper_link) {
                        retries = upper->mp->mnt_unmount_retries;
                        if (retries > deferred_unmount_retry_limit) {
                                error = EBUSY;
                                continue;
                        }
                        MNT_IUNLOCK(mp);

                        vfs_ref(upper->mp);
                        if (!deferred_unmount_enqueue(upper->mp, flags,
                            false, 0))
                                vfs_rel(upper->mp);
                        MNT_ILOCK(mp);
                }
                mp->mnt_upper_pending--;
                if ((mp->mnt_kern_flag & MNTK_UPPER_WAITER) != 0 &&
                    mp->mnt_upper_pending == 0) {
                        mp->mnt_kern_flag &= ~MNTK_UPPER_WAITER;
                        wakeup(&mp->mnt_uppers);
                }

                /*
                 * If we're not on the taskqueue, wait until the uppers list
                 * is drained before proceeding with unmount.  Otherwise, if
                 * we are on the taskqueue and there are still pending uppers,
                 * just re-enqueue on the end of the taskqueue.
                 */
                if ((flags & MNT_DEFERRED) == 0) {
                        while (error == 0 && !TAILQ_EMPTY(&mp->mnt_uppers)) {
                                mp->mnt_kern_flag |= MNTK_TASKQUEUE_WAITER;
                                error = msleep(&mp->mnt_taskqueue_link,
                                    MNT_MTX(mp), PCATCH, "umntqw", 0);
                        }
                        if (error != 0) {
                                MNT_REL(mp);
                                MNT_IUNLOCK(mp);
                                return (error);
                        }
                } else if (!TAILQ_EMPTY(&mp->mnt_uppers)) {
                        MNT_IUNLOCK(mp);
                        if (error == 0)
                                deferred_unmount_enqueue(mp, flags, true, 0);
                        return (error);
                }
                MNT_IUNLOCK(mp);
                KASSERT(TAILQ_EMPTY(&mp->mnt_uppers), ("mnt_uppers not empty"));
        }

        /* Allow the taskqueue to safely re-enqueue on failure */
        if ((flags & MNT_DEFERRED) != 0)
                vfs_ref(mp);

        if ((coveredvp = mp->mnt_vnodecovered) != NULL) {
                mnt_gen_r = mp->mnt_gen;
                VI_LOCK(coveredvp);
                vholdl(coveredvp);
                vn_lock(coveredvp, LK_EXCLUSIVE | LK_INTERLOCK | LK_RETRY);
                /*
                 * Check for mp being unmounted while waiting for the
                 * covered vnode lock.
                 */
                if (coveredvp->v_mountedhere != mp ||
                    coveredvp->v_mountedhere->mnt_gen != mnt_gen_r) {
                        VOP_UNLOCK(coveredvp);
                        vdrop(coveredvp);
                        vfs_rel(mp);
                        return (EBUSY);
                }
        }

        vfs_op_enter(mp);

        vn_start_write(NULL, &mp, V_WAIT);
        MNT_ILOCK(mp);
        if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0 ||
            (mp->mnt_flag & MNT_UPDATE) != 0 ||
            !TAILQ_EMPTY(&mp->mnt_uppers)) {
                dounmount_cleanup(mp, coveredvp, 0);
                return (EBUSY);
        }
        mp->mnt_kern_flag |= MNTK_UNMOUNT;
        rootvp = vfs_cache_root_clear(mp);
        if (coveredvp != NULL)
                vn_seqc_write_begin(coveredvp);
        if (flags & MNT_NONBUSY) {
                MNT_IUNLOCK(mp);
                error = vfs_check_usecounts(mp);
                MNT_ILOCK(mp);
                if (error != 0) {
                        vn_seqc_write_end(coveredvp);
                        dounmount_cleanup(mp, coveredvp, MNTK_UNMOUNT);
                        if (rootvp != NULL) {
                                vn_seqc_write_end(rootvp);
                                vrele(rootvp);
                        }
                        return (error);
                }
        }
        /* Allow filesystems to detect that a forced unmount is in progress. */
        if (flags & MNT_FORCE) {
                mp->mnt_kern_flag |= MNTK_UNMOUNTF;
                MNT_IUNLOCK(mp);
                /*
                 * Must be done after setting MNTK_UNMOUNTF and before
                 * waiting for mnt_lockref to become 0.
                 */
                VFS_PURGE(mp);
                MNT_ILOCK(mp);
        }
        error = 0;
        if (mp->mnt_lockref) {
                mp->mnt_kern_flag |= MNTK_DRAINING;
                error = msleep(&mp->mnt_lockref, MNT_MTX(mp), PVFS,
                    "mount drain", 0);
        }
        MNT_IUNLOCK(mp);
        KASSERT(mp->mnt_lockref == 0,
            ("%s: invalid lock refcount in the drain path @ %s:%d",
            __func__, __FILE__, __LINE__));
        KASSERT(error == 0,
            ("%s: invalid return value for msleep in the drain path @ %s:%d",
            __func__, __FILE__, __LINE__));

        /*
         * We want to keep the vnode around so that we can vn_seqc_write_end
         * after we are done with unmount. Downgrade our reference to a mere
         * hold count so that we don't interefere with anything.
         */
        if (rootvp != NULL) {
                vhold(rootvp);
                vrele(rootvp);
        }

        if (mp->mnt_flag & MNT_EXPUBLIC)
                vfs_setpublicfs(NULL, NULL, NULL);

        vfs_periodic(mp, MNT_WAIT);
        MNT_ILOCK(mp);
        async_flag = mp->mnt_flag & MNT_ASYNC;
        mp->mnt_flag &= ~MNT_ASYNC;
        mp->mnt_kern_flag &= ~MNTK_ASYNC;
        MNT_IUNLOCK(mp);
        vfs_deallocate_syncvnode(mp);
        error = VFS_UNMOUNT(mp, flags);
        vn_finished_write(mp);
        vfs_rel(mp);
        /*
         * If we failed to flush the dirty blocks for this mount point,
         * undo all the cdir/rdir and rootvnode changes we made above.
         * Unless we failed to do so because the device is reporting that
         * it doesn't exist anymore.
         */
        if (error && error != ENXIO) {
                MNT_ILOCK(mp);
                if ((mp->mnt_flag & MNT_RDONLY) == 0) {
                        MNT_IUNLOCK(mp);
                        vfs_allocate_syncvnode(mp);
                        MNT_ILOCK(mp);
                }
                mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
                mp->mnt_flag |= async_flag;
                if ((mp->mnt_flag & MNT_ASYNC) != 0 &&
                    (mp->mnt_kern_flag & MNTK_NOASYNC) == 0)
                        mp->mnt_kern_flag |= MNTK_ASYNC;
                if (mp->mnt_kern_flag & MNTK_MWAIT) {
                        mp->mnt_kern_flag &= ~MNTK_MWAIT;
                        wakeup(mp);
                }
                vfs_op_exit_locked(mp);
                MNT_IUNLOCK(mp);
                if (coveredvp) {
                        vn_seqc_write_end(coveredvp);
                        VOP_UNLOCK(coveredvp);
                        vdrop(coveredvp);
                }
                if (rootvp != NULL) {
                        vn_seqc_write_end(rootvp);
                        vdrop(rootvp);
                }
                return (error);
        }

        mtx_lock(&mountlist_mtx);
        TAILQ_REMOVE(&mountlist, mp, mnt_list);
        mtx_unlock(&mountlist_mtx);
        EVENTHANDLER_DIRECT_INVOKE(vfs_unmounted, mp, td);
        if (coveredvp != NULL) {
                VI_LOCK(coveredvp);
                vn_irflag_unset_locked(coveredvp, VIRF_MOUNTPOINT);
                coveredvp->v_mountedhere = NULL;
                vn_seqc_write_end_locked(coveredvp);
                VI_UNLOCK(coveredvp);
                VOP_UNLOCK(coveredvp);
                vdrop(coveredvp);
        }
        mount_devctl_event("UNMOUNT", mp, false);
        if (rootvp != NULL) {
                vn_seqc_write_end(rootvp);
                vdrop(rootvp);
        }
        vfs_event_signal(NULL, VQ_UNMOUNT, 0);
        if (rootvnode != NULL && mp == rootvnode->v_mount) {
                vrele(rootvnode);
                rootvnode = NULL;
        }
        if (mp == rootdevmp)
                rootdevmp = NULL;
        if ((flags & MNT_DEFERRED) != 0)
                vfs_rel(mp);
        vfs_mount_destroy(mp);
        return (0);
}

/*
 * Report errors during filesystem mounting.
 */
void
vfs_mount_error(struct mount *mp, const char *fmt, ...)
{
        struct vfsoptlist *moptlist = mp->mnt_optnew;
        va_list ap;
        int error, len;
        char *errmsg;

        error = vfs_getopt(moptlist, "errmsg", (void **)&errmsg, &len);
        if (error || errmsg == NULL || len <= 0)
                return;

        va_start(ap, fmt);
        vsnprintf(errmsg, (size_t)len, fmt, ap);
        va_end(ap);
}

void
vfs_opterror(struct vfsoptlist *opts, const char *fmt, ...)
{
        va_list ap;
        int error, len;
        char *errmsg;

        error = vfs_getopt(opts, "errmsg", (void **)&errmsg, &len);
        if (error || errmsg == NULL || len <= 0)
                return;

        va_start(ap, fmt);
        vsnprintf(errmsg, (size_t)len, fmt, ap);
        va_end(ap);
}

/*
 * ---------------------------------------------------------------------
 * Functions for querying mount options/arguments from filesystems.
 */

/*
 * Check that no unknown options are given
 */
int
vfs_filteropt(struct vfsoptlist *opts, const char **legal)
{
        struct vfsopt *opt;
        char errmsg[255];
        const char **t, *p, *q;
        int ret = 0;

        TAILQ_FOREACH(opt, opts, link) {
                p = opt->name;
                q = NULL;
                if (p[0] == 'n' && p[1] == 'o')
                        q = p + 2;
                for(t = global_opts; *t != NULL; t++) {
                        if (strcmp(*t, p) == 0)
                                break;
                        if (q != NULL) {
                                if (strcmp(*t, q) == 0)
                                        break;
                        }
                }
                if (*t != NULL)
                        continue;
                for(t = legal; *t != NULL; t++) {
                        if (strcmp(*t, p) == 0)
                                break;
                        if (q != NULL) {
                                if (strcmp(*t, q) == 0)
                                        break;
                        }
                }
                if (*t != NULL)
                        continue;
                snprintf(errmsg, sizeof(errmsg),
                    "mount option <%s> is unknown", p);
                ret = EINVAL;
        }
        if (ret != 0) {
                TAILQ_FOREACH(opt, opts, link) {
                        if (strcmp(opt->name, "errmsg") == 0) {
                                strncpy((char *)opt->value, errmsg, opt->len);
                                break;
                        }
                }
                if (opt == NULL)
                        printf("%s\n", errmsg);
        }
        return (ret);
}

/*
 * Get a mount option by its name.
 *
 * Return 0 if the option was found, ENOENT otherwise.
 * If len is non-NULL it will be filled with the length
 * of the option. If buf is non-NULL, it will be filled
 * with the address of the option.
 */
int
vfs_getopt(struct vfsoptlist *opts, const char *name, void **buf, int *len)
{
        struct vfsopt *opt;

        KASSERT(opts != NULL, ("vfs_getopt: caller passed 'opts' as NULL"));

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) == 0) {
                        opt->seen = 1;
                        if (len != NULL)
                                *len = opt->len;
                        if (buf != NULL)
                                *buf = opt->value;
                        return (0);
                }
        }
        return (ENOENT);
}

int
vfs_getopt_pos(struct vfsoptlist *opts, const char *name)
{
        struct vfsopt *opt;

        if (opts == NULL)
                return (-1);

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) == 0) {
                        opt->seen = 1;
                        return (opt->pos);
                }
        }
        return (-1);
}

int
vfs_getopt_size(struct vfsoptlist *opts, const char *name, off_t *value)
{
        char *opt_value, *vtp;
        quad_t iv;
        int error, opt_len;

        error = vfs_getopt(opts, name, (void **)&opt_value, &opt_len);
        if (error != 0)
                return (error);
        if (opt_len == 0 || opt_value == NULL)
                return (EINVAL);
        if (opt_value[0] == '\0' || opt_value[opt_len - 1] != '\0')
                return (EINVAL);
        iv = strtoq(opt_value, &vtp, 0);
        if (vtp == opt_value || (vtp[0] != '\0' && vtp[1] != '\0'))
                return (EINVAL);
        if (iv < 0)
                return (EINVAL);
        switch (vtp[0]) {
        case 't': case 'T':
                iv *= 1024;
                /* FALLTHROUGH */
        case 'g': case 'G':
                iv *= 1024;
                /* FALLTHROUGH */
        case 'm': case 'M':
                iv *= 1024;
                /* FALLTHROUGH */
        case 'k': case 'K':
                iv *= 1024;
        case '\0':
                break;
        default:
                return (EINVAL);
        }
        *value = iv;

        return (0);
}

char *
vfs_getopts(struct vfsoptlist *opts, const char *name, int *error)
{
        struct vfsopt *opt;

        *error = 0;
        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) != 0)
                        continue;
                opt->seen = 1;
                if (opt->len == 0 ||
                    ((char *)opt->value)[opt->len - 1] != '\0') {
                        *error = EINVAL;
                        return (NULL);
                }
                return (opt->value);
        }
        *error = ENOENT;
        return (NULL);
}

int
vfs_flagopt(struct vfsoptlist *opts, const char *name, uint64_t *w,
        uint64_t val)
{
        struct vfsopt *opt;

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) == 0) {
                        opt->seen = 1;
                        if (w != NULL)
                                *w |= val;
                        return (1);
                }
        }
        if (w != NULL)
                *w &= ~val;
        return (0);
}

int
vfs_scanopt(struct vfsoptlist *opts, const char *name, const char *fmt, ...)
{
        va_list ap;
        struct vfsopt *opt;
        int ret;

        KASSERT(opts != NULL, ("vfs_getopt: caller passed 'opts' as NULL"));

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) != 0)
                        continue;
                opt->seen = 1;
                if (opt->len == 0 || opt->value == NULL)
                        return (0);
                if (((char *)opt->value)[opt->len - 1] != '\0')
                        return (0);
                va_start(ap, fmt);
                ret = vsscanf(opt->value, fmt, ap);
                va_end(ap);
                return (ret);
        }
        return (0);
}

int
vfs_setopt(struct vfsoptlist *opts, const char *name, void *value, int len)
{
        struct vfsopt *opt;

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) != 0)
                        continue;
                opt->seen = 1;
                if (opt->value == NULL)
                        opt->len = len;
                else {
                        if (opt->len != len)
                                return (EINVAL);
                        bcopy(value, opt->value, len);
                }
                return (0);
        }
        return (ENOENT);
}

int
vfs_setopt_part(struct vfsoptlist *opts, const char *name, void *value, int len)
{
        struct vfsopt *opt;

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) != 0)
                        continue;
                opt->seen = 1;
                if (opt->value == NULL)
                        opt->len = len;
                else {
                        if (opt->len < len)
                                return (EINVAL);
                        opt->len = len;
                        bcopy(value, opt->value, len);
                }
                return (0);
        }
        return (ENOENT);
}

int
vfs_setopts(struct vfsoptlist *opts, const char *name, const char *value)
{
        struct vfsopt *opt;

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) != 0)
                        continue;
                opt->seen = 1;
                if (opt->value == NULL)
                        opt->len = strlen(value) + 1;
                else if (strlcpy(opt->value, value, opt->len) >= opt->len)
                        return (EINVAL);
                return (0);
        }
        return (ENOENT);
}

/*
 * Find and copy a mount option.
 *
 * The size of the buffer has to be specified
 * in len, if it is not the same length as the
 * mount option, EINVAL is returned.
 * Returns ENOENT if the option is not found.
 */
int
vfs_copyopt(struct vfsoptlist *opts, const char *name, void *dest, int len)
{
        struct vfsopt *opt;

        KASSERT(opts != NULL, ("vfs_copyopt: caller passed 'opts' as NULL"));

        TAILQ_FOREACH(opt, opts, link) {
                if (strcmp(name, opt->name) == 0) {
                        opt->seen = 1;
                        if (len != opt->len)
                                return (EINVAL);
                        bcopy(opt->value, dest, opt->len);
                        return (0);
                }
        }
        return (ENOENT);
}

int
__vfs_statfs(struct mount *mp, struct statfs *sbp)
{
        /*
         * Filesystems only fill in part of the structure for updates, we
         * have to read the entirety first to get all content.
         */
        if (sbp != &mp->mnt_stat)
                memcpy(sbp, &mp->mnt_stat, sizeof(*sbp));

        /*
         * Set these in case the underlying filesystem fails to do so.
         */
        sbp->f_version = STATFS_VERSION;
        sbp->f_namemax = NAME_MAX;
        sbp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
        sbp->f_nvnodelistsize = mp->mnt_nvnodelistsize;

        return (mp->mnt_op->vfs_statfs(mp, sbp));
}

void
vfs_mountedfrom(struct mount *mp, const char *from)
{

        bzero(mp->mnt_stat.f_mntfromname, sizeof mp->mnt_stat.f_mntfromname);
        strlcpy(mp->mnt_stat.f_mntfromname, from,
            sizeof mp->mnt_stat.f_mntfromname);
}

/*
 * ---------------------------------------------------------------------
 * This is the api for building mount args and mounting filesystems from
 * inside the kernel.
 *
 * The API works by accumulation of individual args.  First error is
 * latched.
 *
 * XXX: should be documented in new manpage kernel_mount(9)
 */

/* A memory allocation which must be freed when we are done */
struct mntaarg {
        SLIST_ENTRY(mntaarg)    next;
};

/* The header for the mount arguments */
struct mntarg {
        struct iovec *v;
        int len;
        int error;
        SLIST_HEAD(, mntaarg)   list;
};

/*
 * Add a boolean argument.
 *
 * flag is the boolean value.
 * name must start with "no".
 */
struct mntarg *
mount_argb(struct mntarg *ma, int flag, const char *name)
{

        KASSERT(name[0] == 'n' && name[1] == 'o',
            ("mount_argb(...,%s): name must start with 'no'", name));

        return (mount_arg(ma, name + (flag ? 2 : 0), NULL, 0));
}

/*
 * Add an argument printf style
 */
struct mntarg *
mount_argf(struct mntarg *ma, const char *name, const char *fmt, ...)
{
        va_list ap;
        struct mntaarg *maa;
        struct sbuf *sb;
        int len;

        if (ma == NULL) {
                ma = malloc(sizeof *ma, M_MOUNT, M_WAITOK | M_ZERO);
                SLIST_INIT(&ma->list);
        }
        if (ma->error)
                return (ma);

        ma->v = realloc(ma->v, sizeof *ma->v * (ma->len + 2),
            M_MOUNT, M_WAITOK);
        ma->v[ma->len].iov_base = (void *)(uintptr_t)name;
        ma->v[ma->len].iov_len = strlen(name) + 1;
        ma->len++;

        sb = sbuf_new_auto();
        va_start(ap, fmt);
        sbuf_vprintf(sb, fmt, ap);
        va_end(ap);
        sbuf_finish(sb);
        len = sbuf_len(sb) + 1;
        maa = malloc(sizeof *maa + len, M_MOUNT, M_WAITOK | M_ZERO);
        SLIST_INSERT_HEAD(&ma->list, maa, next);
        bcopy(sbuf_data(sb), maa + 1, len);
        sbuf_delete(sb);

        ma->v[ma->len].iov_base = maa + 1;
        ma->v[ma->len].iov_len = len;
        ma->len++;

        return (ma);
}

/*
 * Add an argument which is a userland string.
 */
struct mntarg *
mount_argsu(struct mntarg *ma, const char *name, const void *val, int len)
{
        struct mntaarg *maa;
        char *tbuf;

        if (val == NULL)
                return (ma);
        if (ma == NULL) {
                ma = malloc(sizeof *ma, M_MOUNT, M_WAITOK | M_ZERO);
                SLIST_INIT(&ma->list);
        }
        if (ma->error)
                return (ma);
        maa = malloc(sizeof *maa + len, M_MOUNT, M_WAITOK | M_ZERO);
        SLIST_INSERT_HEAD(&ma->list, maa, next);
        tbuf = (void *)(maa + 1);
        ma->error = copyinstr(val, tbuf, len, NULL);
        return (mount_arg(ma, name, tbuf, -1));
}

/*
 * Plain argument.
 *
 * If length is -1, treat value as a C string.
 */
struct mntarg *
mount_arg(struct mntarg *ma, const char *name, const void *val, int len)
{

        if (ma == NULL) {
                ma = malloc(sizeof *ma, M_MOUNT, M_WAITOK | M_ZERO);
                SLIST_INIT(&ma->list);
        }
        if (ma->error)
                return (ma);

        ma->v = realloc(ma->v, sizeof *ma->v * (ma->len + 2),
            M_MOUNT, M_WAITOK);
        ma->v[ma->len].iov_base = (void *)(uintptr_t)name;
        ma->v[ma->len].iov_len = strlen(name) + 1;
        ma->len++;

        ma->v[ma->len].iov_base = (void *)(uintptr_t)val;
        if (len < 0)
                ma->v[ma->len].iov_len = strlen(val) + 1;
        else
                ma->v[ma->len].iov_len = len;
        ma->len++;
        return (ma);
}

/*
 * Free a mntarg structure
 */
static void
free_mntarg(struct mntarg *ma)
{
        struct mntaarg *maa;

        while (!SLIST_EMPTY(&ma->list)) {
                maa = SLIST_FIRST(&ma->list);
                SLIST_REMOVE_HEAD(&ma->list, next);
                free(maa, M_MOUNT);
        }
        free(ma->v, M_MOUNT);
        free(ma, M_MOUNT);
}

/*
 * Mount a filesystem
 */
int
kernel_mount(struct mntarg *ma, uint64_t flags)
{
        struct uio auio;
        int error;

        KASSERT(ma != NULL, ("kernel_mount NULL ma"));
        KASSERT(ma->error != 0 || ma->v != NULL, ("kernel_mount NULL ma->v"));
        KASSERT(!(ma->len & 1), ("kernel_mount odd ma->len (%d)", ma->len));

        error = ma->error;
        if (error == 0) {
                auio.uio_iov = ma->v;
                auio.uio_iovcnt = ma->len;
                auio.uio_segflg = UIO_SYSSPACE;
                error = vfs_donmount(curthread, flags, &auio);
        }
        free_mntarg(ma);
        return (error);
}

/* Map from mount options to printable formats. */
static struct mntoptnames optnames[] = {
        MNTOPT_NAMES
};

#define DEVCTL_LEN 1024
static void
mount_devctl_event(const char *type, struct mount *mp, bool donew)
{
        const uint8_t *cp;
        struct mntoptnames *fp;
        struct sbuf sb;
        struct statfs *sfp = &mp->mnt_stat;
        char *buf;

        buf = malloc(DEVCTL_LEN, M_MOUNT, M_NOWAIT);
        if (buf == NULL)
                return;
        sbuf_new(&sb, buf, DEVCTL_LEN, SBUF_FIXEDLEN);
        sbuf_cpy(&sb, "mount-point=\"");
        devctl_safe_quote_sb(&sb, sfp->f_mntonname);
        sbuf_cat(&sb, "\" mount-dev=\"");
        devctl_safe_quote_sb(&sb, sfp->f_mntfromname);
        sbuf_cat(&sb, "\" mount-type=\"");
        devctl_safe_quote_sb(&sb, sfp->f_fstypename);
        sbuf_cat(&sb, "\" fsid=0x");
        cp = (const uint8_t *)&sfp->f_fsid.val[0];
        for (int i = 0; i < sizeof(sfp->f_fsid); i++)
                sbuf_printf(&sb, "%02x", cp[i]);
        sbuf_printf(&sb, " owner=%u flags=\"", sfp->f_owner);
        for (fp = optnames; fp->o_opt != 0; fp++) {
                if ((mp->mnt_flag & fp->o_opt) != 0) {
                        sbuf_cat(&sb, fp->o_name);
                        sbuf_putc(&sb, ';');
                }
        }
        sbuf_putc(&sb, '"');
        sbuf_finish(&sb);

        /*
         * Options are not published because the form of the options depends on
         * the file system and may include binary data. In addition, they don't
         * necessarily provide enough useful information to be actionable when
         * devd processes them.
         */

        if (sbuf_error(&sb) == 0)
                devctl_notify("VFS", "FS", type, sbuf_data(&sb));
        sbuf_delete(&sb);
        free(buf, M_MOUNT);
}

/*
 * Force remount specified mount point to read-only.  The argument
 * must be busied to avoid parallel unmount attempts.
 *
 * Intended use is to prevent further writes if some metadata
 * inconsistency is detected.  Note that the function still flushes
 * all cached metadata and data for the mount point, which might be
 * not always suitable.
 */
int
vfs_remount_ro(struct mount *mp)
{
        struct vfsoptlist *opts;
        struct vfsopt *opt;
        struct vnode *vp_covered, *rootvp;
        int error;

        vfs_op_enter(mp);
        KASSERT(mp->mnt_lockref > 0,
            ("vfs_remount_ro: mp %p is not busied", mp));
        KASSERT((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0,
            ("vfs_remount_ro: mp %p is being unmounted (and busy?)", mp));

        rootvp = NULL;
        vp_covered = mp->mnt_vnodecovered;
        error = vget(vp_covered, LK_EXCLUSIVE | LK_NOWAIT);
        if (error != 0) {
                vfs_op_exit(mp);
                return (error);
        }
        VI_LOCK(vp_covered);
        if ((vp_covered->v_iflag & VI_MOUNT) != 0) {
                VI_UNLOCK(vp_covered);
                vput(vp_covered);
                vfs_op_exit(mp);
                return (EBUSY);
        }
        vp_covered->v_iflag |= VI_MOUNT;
        VI_UNLOCK(vp_covered);
        vn_seqc_write_begin(vp_covered);

        MNT_ILOCK(mp);
        if ((mp->mnt_flag & MNT_RDONLY) != 0) {
                MNT_IUNLOCK(mp);
                error = EBUSY;
                goto out;
        }
        mp->mnt_flag |= MNT_UPDATE | MNT_FORCE | MNT_RDONLY;
        rootvp = vfs_cache_root_clear(mp);
        MNT_IUNLOCK(mp);

        opts = malloc(sizeof(struct vfsoptlist), M_MOUNT, M_WAITOK | M_ZERO);
        TAILQ_INIT(opts);
        opt = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK | M_ZERO);
        opt->name = strdup("ro", M_MOUNT);
        opt->value = NULL;
        TAILQ_INSERT_TAIL(opts, opt, link);
        vfs_mergeopts(opts, mp->mnt_opt);
        mp->mnt_optnew = opts;

        error = VFS_MOUNT(mp);

        if (error == 0) {
                MNT_ILOCK(mp);
                mp->mnt_flag &= ~(MNT_UPDATE | MNT_FORCE);
                MNT_IUNLOCK(mp);
                vfs_deallocate_syncvnode(mp);
                if (mp->mnt_opt != NULL)
                        vfs_freeopts(mp->mnt_opt);
                mp->mnt_opt = mp->mnt_optnew;
        } else {
                MNT_ILOCK(mp);
                mp->mnt_flag &= ~(MNT_UPDATE | MNT_FORCE | MNT_RDONLY);
                MNT_IUNLOCK(mp);
                vfs_freeopts(mp->mnt_optnew);
        }
        mp->mnt_optnew = NULL;

out:
        vfs_op_exit(mp);
        VI_LOCK(vp_covered);
        vp_covered->v_iflag &= ~VI_MOUNT;
        VI_UNLOCK(vp_covered);
        vput(vp_covered);
        vn_seqc_write_end(vp_covered);
        if (rootvp != NULL) {
                vn_seqc_write_end(rootvp);
                vrele(rootvp);
        }
        return (error);
}

/*
 * Suspend write operations on all local writeable filesystems.  Does
 * full sync of them in the process.
 *
 * Iterate over the mount points in reverse order, suspending most
 * recently mounted filesystems first.  It handles a case where a
 * filesystem mounted from a md(4) vnode-backed device should be
 * suspended before the filesystem that owns the vnode.
 */
void
suspend_all_fs(void)
{
        struct mount *mp;
        int error;

        mtx_lock(&mountlist_mtx);
        TAILQ_FOREACH_REVERSE(mp, &mountlist, mntlist, mnt_list) {
                error = vfs_busy(mp, MBF_MNTLSTLOCK | MBF_NOWAIT);
                if (error != 0)
                        continue;
                if ((mp->mnt_flag & (MNT_RDONLY | MNT_LOCAL)) != MNT_LOCAL ||
                    (mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
                        mtx_lock(&mountlist_mtx);
                        vfs_unbusy(mp);
                        continue;
                }
                error = vfs_write_suspend(mp, 0);
                if (error == 0) {
                        MNT_ILOCK(mp);
                        MPASS((mp->mnt_kern_flag & MNTK_SUSPEND_ALL) == 0);
                        mp->mnt_kern_flag |= MNTK_SUSPEND_ALL;
                        MNT_IUNLOCK(mp);
                        mtx_lock(&mountlist_mtx);
                } else {
                        printf("suspend of %s failed, error %d\n",
                            mp->mnt_stat.f_mntonname, error);
                        mtx_lock(&mountlist_mtx);
                        vfs_unbusy(mp);
                }
        }
        mtx_unlock(&mountlist_mtx);
}

/*
 * Clone the mnt_exjail field to a new mount point.
 */
void
vfs_exjail_clone(struct mount *inmp, struct mount *outmp)
{
        struct ucred *cr;
        struct prison *pr;

        MNT_ILOCK(inmp);
        cr = inmp->mnt_exjail;
        if (cr != NULL) {
                crhold(cr);
                MNT_IUNLOCK(inmp);
                pr = cr->cr_prison;
                sx_slock(&allprison_lock);
                if (!prison_isalive(pr)) {
                        sx_sunlock(&allprison_lock);
                        crfree(cr);
                        return;
                }
                MNT_ILOCK(outmp);
                if (outmp->mnt_exjail == NULL) {
                        outmp->mnt_exjail = cr;
                        atomic_add_int(&pr->pr_exportcnt, 1);
                        cr = NULL;
                }
                MNT_IUNLOCK(outmp);
                sx_sunlock(&allprison_lock);
                if (cr != NULL)
                        crfree(cr);
        } else
                MNT_IUNLOCK(inmp);
}

void
resume_all_fs(void)
{
        struct mount *mp;

        mtx_lock(&mountlist_mtx);
        TAILQ_FOREACH(mp, &mountlist, mnt_list) {
                if ((mp->mnt_kern_flag & MNTK_SUSPEND_ALL) == 0)
                        continue;
                mtx_unlock(&mountlist_mtx);
                MNT_ILOCK(mp);
                MPASS((mp->mnt_kern_flag & MNTK_SUSPEND) != 0);
                mp->mnt_kern_flag &= ~MNTK_SUSPEND_ALL;
                MNT_IUNLOCK(mp);
                vfs_write_resume(mp, 0);
                mtx_lock(&mountlist_mtx);
                vfs_unbusy(mp);
        }
        mtx_unlock(&mountlist_mtx);
}