fs/zfs/zfs_vfsops.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysmacros.h>
#include <sys/kmem.h>
#include <sys/pathname.h>
#include <sys/vnode.h>
#include <sys/vfs.h>
#include <sys/vfs_opreg.h>
#include <sys/mntent.h>
#include <sys/mount.h>
#include <sys/cmn_err.h>
#include "fs/fs_subr.h"
#include <sys/zfs_znode.h>
#include <sys/zfs_dir.h>
#include <sys/zil.h>
#include <sys/fs/zfs.h>
#include <sys/dmu.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_deleg.h>
#include <sys/spa.h>
#include <sys/zap.h>
#include <sys/varargs.h>
#include <sys/policy.h>
#include <sys/atomic.h>
#include <sys/mkdev.h>
#include <sys/modctl.h>
#include <sys/refstr.h>
#include <sys/zfs_ioctl.h>
#include <sys/zfs_ctldir.h>
#include <sys/zfs_fuid.h>
#include <sys/bootconf.h>
#include <sys/sunddi.h>
#include <sys/dnlc.h>
#include <sys/dmu_objset.h>
#include <sys/spa_boot.h>

int zfsfstype;
vfsops_t *zfs_vfsops = NULL;
static major_t zfs_major;
static minor_t zfs_minor;
static kmutex_t	zfs_dev_mtx;

static int zfs_mount(vfs_t *vfsp, vnode_t *mvp, struct mounta *uap, cred_t *cr);
static int zfs_umount(vfs_t *vfsp, int fflag, cred_t *cr);
static int zfs_mountroot(vfs_t *vfsp, enum whymountroot);
static int zfs_root(vfs_t *vfsp, vnode_t **vpp);
static int zfs_statvfs(vfs_t *vfsp, struct statvfs64 *statp);
static int zfs_vget(vfs_t *vfsp, vnode_t **vpp, fid_t *fidp);
static void zfs_freevfs(vfs_t *vfsp);

static const fs_operation_def_t zfs_vfsops_template[] = {
	VFSNAME_MOUNT,		{ .vfs_mount = zfs_mount },
	VFSNAME_MOUNTROOT,	{ .vfs_mountroot = zfs_mountroot },
	VFSNAME_UNMOUNT,	{ .vfs_unmount = zfs_umount },
	VFSNAME_ROOT,		{ .vfs_root = zfs_root },
	VFSNAME_STATVFS,	{ .vfs_statvfs = zfs_statvfs },
	VFSNAME_SYNC,		{ .vfs_sync = zfs_sync },
	VFSNAME_VGET,		{ .vfs_vget = zfs_vget },
	VFSNAME_FREEVFS,	{ .vfs_freevfs = zfs_freevfs },
	NULL,			NULL
};

static const fs_operation_def_t zfs_vfsops_eio_template[] = {
	VFSNAME_FREEVFS,	{ .vfs_freevfs =  zfs_freevfs },
	NULL,			NULL
};

/*
 * We need to keep a count of active fs's.
 * This is necessary to prevent our module
 * from being unloaded after a umount -f
 */
static uint32_t	zfs_active_fs_count = 0;

static char *noatime_cancel[] = { MNTOPT_ATIME, NULL };
static char *atime_cancel[] = { MNTOPT_NOATIME, NULL };
static char *noxattr_cancel[] = { MNTOPT_XATTR, NULL };
static char *xattr_cancel[] = { MNTOPT_NOXATTR, NULL };

/*
 * MO_DEFAULT is not used since the default value is determined
 * by the equivalent property.
 */
static mntopt_t mntopts[] = {
	{ MNTOPT_NOXATTR, noxattr_cancel, NULL, 0, NULL },
	{ MNTOPT_XATTR, xattr_cancel, NULL, 0, NULL },
	{ MNTOPT_NOATIME, noatime_cancel, NULL, 0, NULL },
	{ MNTOPT_ATIME, atime_cancel, NULL, 0, NULL }
};

static mntopts_t zfs_mntopts = {
	sizeof (mntopts) / sizeof (mntopt_t),
	mntopts
};

/*ARGSUSED*/
int
zfs_sync(vfs_t *vfsp, short flag, cred_t *cr)
{
	/*
	 * Data integrity is job one.  We don't want a compromised kernel
	 * writing to the storage pool, so we never sync during panic.
	 */
	if (panicstr)
		return (0);

	/*
	 * SYNC_ATTR is used by fsflush() to force old filesystems like UFS
	 * to sync metadata, which they would otherwise cache indefinitely.
	 * Semantically, the only requirement is that the sync be initiated.
	 * The DMU syncs out txgs frequently, so there's nothing to do.
	 */
	if (flag & SYNC_ATTR)
		return (0);

	if (vfsp != NULL) {
		/*
		 * Sync a specific filesystem.
		 */
		zfsvfs_t *zfsvfs = vfsp->vfs_data;

		ZFS_ENTER(zfsvfs);
		if (zfsvfs->z_log != NULL)
			zil_commit(zfsvfs->z_log, UINT64_MAX, 0);
		else
			txg_wait_synced(dmu_objset_pool(zfsvfs->z_os), 0);
		ZFS_EXIT(zfsvfs);
	} else {
		/*
		 * Sync all ZFS filesystems.  This is what happens when you
		 * run sync(1M).  Unlike other filesystems, ZFS honors the
		 * request by waiting for all pools to commit all dirty data.
		 */
		spa_sync_allpools();
	}

	return (0);
}

static int
zfs_create_unique_device(dev_t *dev)
{
	major_t new_major;

	do {
		ASSERT3U(zfs_minor, <=, MAXMIN32);
		minor_t start = zfs_minor;
		do {
			mutex_enter(&zfs_dev_mtx);
			if (zfs_minor >= MAXMIN32) {
				/*
				 * If we're still using the real major
				 * keep out of /dev/zfs and /dev/zvol minor
				 * number space.  If we're using a getudev()'ed
				 * major number, we can use all of its minors.
				 */
				if (zfs_major == ddi_name_to_major(ZFS_DRIVER))
					zfs_minor = ZFS_MIN_MINOR;
				else
					zfs_minor = 0;
			} else {
				zfs_minor++;
			}
			*dev = makedevice(zfs_major, zfs_minor);
			mutex_exit(&zfs_dev_mtx);
		} while (vfs_devismounted(*dev) && zfs_minor != start);
		if (zfs_minor == start) {
			/*
			 * We are using all ~262,000 minor numbers for the
			 * current major number.  Create a new major number.
			 */
			if ((new_major = getudev()) == (major_t)-1) {
				cmn_err(CE_WARN,
				    "zfs_mount: Can't get unique major "
				    "device number.");
				return (-1);
			}
			mutex_enter(&zfs_dev_mtx);
			zfs_major = new_major;
			zfs_minor = 0;

			mutex_exit(&zfs_dev_mtx);
		} else {
			break;
		}
		/* CONSTANTCONDITION */
	} while (1);

	return (0);
}

static void
atime_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval == TRUE) {
		zfsvfs->z_atime = TRUE;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NOATIME);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_ATIME, NULL, 0);
	} else {
		zfsvfs->z_atime = FALSE;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_ATIME);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NOATIME, NULL, 0);
	}
}

static void
xattr_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval == TRUE) {
		/* XXX locking on vfs_flag? */
		zfsvfs->z_vfs->vfs_flag |= VFS_XATTR;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NOXATTR);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_XATTR, NULL, 0);
	} else {
		/* XXX locking on vfs_flag? */
		zfsvfs->z_vfs->vfs_flag &= ~VFS_XATTR;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_XATTR);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NOXATTR, NULL, 0);
	}
}

static void
blksz_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval < SPA_MINBLOCKSIZE ||
	    newval > SPA_MAXBLOCKSIZE || !ISP2(newval))
		newval = SPA_MAXBLOCKSIZE;

	zfsvfs->z_max_blksz = newval;
	zfsvfs->z_vfs->vfs_bsize = newval;
}

static void
readonly_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval) {
		/* XXX locking on vfs_flag? */
		zfsvfs->z_vfs->vfs_flag |= VFS_RDONLY;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_RW);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_RO, NULL, 0);
	} else {
		/* XXX locking on vfs_flag? */
		zfsvfs->z_vfs->vfs_flag &= ~VFS_RDONLY;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_RO);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_RW, NULL, 0);
	}
}

static void
devices_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval == FALSE) {
		zfsvfs->z_vfs->vfs_flag |= VFS_NODEVICES;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_DEVICES);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NODEVICES, NULL, 0);
	} else {
		zfsvfs->z_vfs->vfs_flag &= ~VFS_NODEVICES;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NODEVICES);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_DEVICES, NULL, 0);
	}
}

static void
setuid_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval == FALSE) {
		zfsvfs->z_vfs->vfs_flag |= VFS_NOSETUID;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_SETUID);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NOSETUID, NULL, 0);
	} else {
		zfsvfs->z_vfs->vfs_flag &= ~VFS_NOSETUID;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NOSETUID);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_SETUID, NULL, 0);
	}
}

static void
exec_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	if (newval == FALSE) {
		zfsvfs->z_vfs->vfs_flag |= VFS_NOEXEC;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_EXEC);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NOEXEC, NULL, 0);
	} else {
		zfsvfs->z_vfs->vfs_flag &= ~VFS_NOEXEC;
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NOEXEC);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_EXEC, NULL, 0);
	}
}

/*
 * The nbmand mount option can be changed at mount time.
 * We can't allow it to be toggled on live file systems or incorrect
 * behavior may be seen from cifs clients
 *
 * This property isn't registered via dsl_prop_register(), but this callback
 * will be called when a file system is first mounted
 */
static void
nbmand_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;
	if (newval == FALSE) {
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NBMAND);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NONBMAND, NULL, 0);
	} else {
		vfs_clearmntopt(zfsvfs->z_vfs, MNTOPT_NONBMAND);
		vfs_setmntopt(zfsvfs->z_vfs, MNTOPT_NBMAND, NULL, 0);
	}
}

static void
snapdir_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	zfsvfs->z_show_ctldir = newval;
}

static void
vscan_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	zfsvfs->z_vscan = newval;
}

static void
acl_mode_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	zfsvfs->z_acl_mode = newval;
}

static void
acl_inherit_changed_cb(void *arg, uint64_t newval)
{
	zfsvfs_t *zfsvfs = arg;

	zfsvfs->z_acl_inherit = newval;
}

static int
zfs_register_callbacks(vfs_t *vfsp)
{
	struct dsl_dataset *ds = NULL;
	objset_t *os = NULL;
	zfsvfs_t *zfsvfs = NULL;
	uint64_t nbmand;
	int readonly, do_readonly = B_FALSE;
	int setuid, do_setuid = B_FALSE;
	int exec, do_exec = B_FALSE;
	int devices, do_devices = B_FALSE;
	int xattr, do_xattr = B_FALSE;
	int atime, do_atime = B_FALSE;
	int error = 0;

	ASSERT(vfsp);
	zfsvfs = vfsp->vfs_data;
	ASSERT(zfsvfs);
	os = zfsvfs->z_os;

	/*
	 * The act of registering our callbacks will destroy any mount
	 * options we may have.  In order to enable temporary overrides
	 * of mount options, we stash away the current values and
	 * restore them after we register the callbacks.
	 */
	if (vfs_optionisset(vfsp, MNTOPT_RO, NULL)) {
		readonly = B_TRUE;
		do_readonly = B_TRUE;
	} else if (vfs_optionisset(vfsp, MNTOPT_RW, NULL)) {
		readonly = B_FALSE;
		do_readonly = B_TRUE;
	}
	if (vfs_optionisset(vfsp, MNTOPT_NOSUID, NULL)) {
		devices = B_FALSE;
		setuid = B_FALSE;
		do_devices = B_TRUE;
		do_setuid = B_TRUE;
	} else {
		if (vfs_optionisset(vfsp, MNTOPT_NODEVICES, NULL)) {
			devices = B_FALSE;
			do_devices = B_TRUE;
		} else if (vfs_optionisset(vfsp, MNTOPT_DEVICES, NULL)) {
			devices = B_TRUE;
			do_devices = B_TRUE;
		}

		if (vfs_optionisset(vfsp, MNTOPT_NOSETUID, NULL)) {
			setuid = B_FALSE;
			do_setuid = B_TRUE;
		} else if (vfs_optionisset(vfsp, MNTOPT_SETUID, NULL)) {
			setuid = B_TRUE;
			do_setuid = B_TRUE;
		}
	}
	if (vfs_optionisset(vfsp, MNTOPT_NOEXEC, NULL)) {
		exec = B_FALSE;
		do_exec = B_TRUE;
	} else if (vfs_optionisset(vfsp, MNTOPT_EXEC, NULL)) {
		exec = B_TRUE;
		do_exec = B_TRUE;
	}
	if (vfs_optionisset(vfsp, MNTOPT_NOXATTR, NULL)) {
		xattr = B_FALSE;
		do_xattr = B_TRUE;
	} else if (vfs_optionisset(vfsp, MNTOPT_XATTR, NULL)) {
		xattr = B_TRUE;
		do_xattr = B_TRUE;
	}
	if (vfs_optionisset(vfsp, MNTOPT_NOATIME, NULL)) {
		atime = B_FALSE;
		do_atime = B_TRUE;
	} else if (vfs_optionisset(vfsp, MNTOPT_ATIME, NULL)) {
		atime = B_TRUE;
		do_atime = B_TRUE;
	}

	/*
	 * nbmand is a special property.  It can only be changed at
	 * mount time.
	 *
	 * This is weird, but it is documented to only be changeable
	 * at mount time.
	 */
	if (vfs_optionisset(vfsp, MNTOPT_NONBMAND, NULL)) {
		nbmand = B_FALSE;
	} else if (vfs_optionisset(vfsp, MNTOPT_NBMAND, NULL)) {
		nbmand = B_TRUE;
	} else {
		char osname[MAXNAMELEN];

		dmu_objset_name(os, osname);
		if (error = dsl_prop_get_integer(osname, "nbmand", &nbmand,
		    NULL)) {
			return (error);
		}
	}

	/*
	 * Register property callbacks.
	 *
	 * It would probably be fine to just check for i/o error from
	 * the first prop_register(), but I guess I like to go
	 * overboard...
	 */
	ds = dmu_objset_ds(os);
	error = dsl_prop_register(ds, "atime", atime_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "xattr", xattr_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "recordsize", blksz_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "readonly", readonly_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "devices", devices_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "setuid", setuid_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "exec", exec_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "snapdir", snapdir_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "aclmode", acl_mode_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "aclinherit", acl_inherit_changed_cb, zfsvfs);
	error = error ? error : dsl_prop_register(ds,
	    "vscan", vscan_changed_cb, zfsvfs);
	if (error)
		goto unregister;

	/*
	 * Invoke our callbacks to restore temporary mount options.
	 */
	if (do_readonly)
		readonly_changed_cb(zfsvfs, readonly);
	if (do_setuid)
		setuid_changed_cb(zfsvfs, setuid);
	if (do_exec)
		exec_changed_cb(zfsvfs, exec);
	if (do_devices)
		devices_changed_cb(zfsvfs, devices);
	if (do_xattr)
		xattr_changed_cb(zfsvfs, xattr);
	if (do_atime)
		atime_changed_cb(zfsvfs, atime);

	nbmand_changed_cb(zfsvfs, nbmand);

	return (0);

unregister:
	/*
	 * We may attempt to unregister some callbacks that are not
	 * registered, but this is OK; it will simply return ENOMSG,
	 * which we will ignore.
	 */
	(void) dsl_prop_unregister(ds, "atime", atime_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "xattr", xattr_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "recordsize", blksz_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "readonly", readonly_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "devices", devices_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "setuid", setuid_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "exec", exec_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "snapdir", snapdir_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "aclmode", acl_mode_changed_cb, zfsvfs);
	(void) dsl_prop_unregister(ds, "aclinherit", acl_inherit_changed_cb,
	    zfsvfs);
	(void) dsl_prop_unregister(ds, "vscan", vscan_changed_cb, zfsvfs);
	return (error);

}

static int
zfsvfs_setup(zfsvfs_t *zfsvfs, boolean_t mounting)
{
	int error;

	error = zfs_register_callbacks(zfsvfs->z_vfs);
	if (error)
		return (error);

	/*
	 * Set the objset user_ptr to track its zfsvfs.
	 */
	mutex_enter(&zfsvfs->z_os->os->os_user_ptr_lock);
	dmu_objset_set_user(zfsvfs->z_os, zfsvfs);
	mutex_exit(&zfsvfs->z_os->os->os_user_ptr_lock);

	/*
	 * If we are not mounting (ie: online recv), then we don't
	 * have to worry about replaying the log as we blocked all
	 * operations out since we closed the ZIL.
	 */
	if (mounting) {
		boolean_t readonly;

		/*
		 * During replay we remove the read only flag to
		 * allow replays to succeed.
		 */
		readonly = zfsvfs->z_vfs->vfs_flag & VFS_RDONLY;
		if (readonly != 0)
			zfsvfs->z_vfs->vfs_flag &= ~VFS_RDONLY;
		else
			zfs_unlinked_drain(zfsvfs);

		zfsvfs->z_log = zil_open(zfsvfs->z_os, zfs_get_data);
		if (zil_disable) {
			zil_destroy(zfsvfs->z_log, 0);
			zfsvfs->z_log = NULL;
		} else {
			/*
			 * Parse and replay the intent log.
			 *
			 * Because of ziltest, this must be done after
			 * zfs_unlinked_drain().  (Further note: ziltest
			 * doesn't use readonly mounts, where
			 * zfs_unlinked_drain() isn't called.)  This is because
			 * ziltest causes spa_sync() to think it's committed,
			 * but actually it is not, so the intent log contains
			 * many txg's worth of changes.
			 *
			 * In particular, if object N is in the unlinked set in
			 * the last txg to actually sync, then it could be
			 * actually freed in a later txg and then reallocated
			 * in a yet later txg.  This would write a "create
			 * object N" record to the intent log.  Normally, this
			 * would be fine because the spa_sync() would have
			 * written out the fact that object N is free, before
			 * we could write the "create object N" intent log
			 * record.
			 *
			 * But when we are in ziltest mode, we advance the "open
			 * txg" without actually spa_sync()-ing the changes to
			 * disk.  So we would see that object N is still
			 * allocated and in the unlinked set, and there is an
			 * intent log record saying to allocate it.
			 */
			zfsvfs->z_replay = B_TRUE;
			zil_replay(zfsvfs->z_os, zfsvfs, zfs_replay_vector);
			zfsvfs->z_replay = B_FALSE;
		}
		zfsvfs->z_vfs->vfs_flag |= readonly; /* restore readonly bit */
	}

	return (0);
}

static void
zfs_freezfsvfs(zfsvfs_t *zfsvfs)
{
	mutex_destroy(&zfsvfs->z_znodes_lock);
	mutex_destroy(&zfsvfs->z_online_recv_lock);
	list_destroy(&zfsvfs->z_all_znodes);
	rrw_destroy(&zfsvfs->z_teardown_lock);
	rw_destroy(&zfsvfs->z_teardown_inactive_lock);
	rw_destroy(&zfsvfs->z_fuid_lock);
	kmem_free(zfsvfs, sizeof (zfsvfs_t));
}

static int
zfs_domount(vfs_t *vfsp, char *osname)
{
	dev_t mount_dev;
	uint64_t recordsize, readonly;
	int error = 0;
	int mode;
	zfsvfs_t *zfsvfs;
	znode_t *zp = NULL;

	ASSERT(vfsp);
	ASSERT(osname);

	/*
	 * Initialize the zfs-specific filesystem structure.
	 * Should probably make this a kmem cache, shuffle fields,
	 * and just bzero up to z_hold_mtx[].
	 */
	zfsvfs = kmem_zalloc(sizeof (zfsvfs_t), KM_SLEEP);
	zfsvfs->z_vfs = vfsp;
	zfsvfs->z_parent = zfsvfs;
	zfsvfs->z_max_blksz = SPA_MAXBLOCKSIZE;
	zfsvfs->z_show_ctldir = ZFS_SNAPDIR_VISIBLE;

	mutex_init(&zfsvfs->z_znodes_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&zfsvfs->z_online_recv_lock, NULL, MUTEX_DEFAULT, NULL);
	list_create(&zfsvfs->z_all_znodes, sizeof (znode_t),
	    offsetof(znode_t, z_link_node));
	rrw_init(&zfsvfs->z_teardown_lock);
	rw_init(&zfsvfs->z_teardown_inactive_lock, NULL, RW_DEFAULT, NULL);
	rw_init(&zfsvfs->z_fuid_lock, NULL, RW_DEFAULT, NULL);

	/* Initialize the generic filesystem structure. */
	vfsp->vfs_bcount = 0;
	vfsp->vfs_data = NULL;

	if (zfs_create_unique_device(&mount_dev) == -1) {
		error = ENODEV;
		goto out;
	}
	ASSERT(vfs_devismounted(mount_dev) == 0);

	if (error = dsl_prop_get_integer(osname, "recordsize", &recordsize,
	    NULL))
		goto out;

	vfsp->vfs_dev = mount_dev;
	vfsp->vfs_fstype = zfsfstype;
	vfsp->vfs_bsize = recordsize;
	vfsp->vfs_flag |= VFS_NOTRUNC;
	vfsp->vfs_data = zfsvfs;

	if (error = dsl_prop_get_integer(osname, "readonly", &readonly, NULL))
		goto out;

	mode = DS_MODE_OWNER;
	if (readonly)
		mode |= DS_MODE_READONLY;

	error = dmu_objset_open(osname, DMU_OST_ZFS, mode, &zfsvfs->z_os);
	if (error == EROFS) {
		mode = DS_MODE_OWNER | DS_MODE_READONLY;
		error = dmu_objset_open(osname, DMU_OST_ZFS, mode,
		    &zfsvfs->z_os);
	}

	if (error)
		goto out;

	if (error = zfs_init_fs(zfsvfs, &zp))
		goto out;

	/* The call to zfs_init_fs leaves the vnode held, release it here. */
	VN_RELE(ZTOV(zp));

	/*
	 * Set features for file system.
	 */
	zfsvfs->z_use_fuids = USE_FUIDS(zfsvfs->z_version, zfsvfs->z_os);
	if (zfsvfs->z_use_fuids) {
		vfs_set_feature(vfsp, VFSFT_XVATTR);
		vfs_set_feature(vfsp, VFSFT_SYSATTR_VIEWS);
		vfs_set_feature(vfsp, VFSFT_ACEMASKONACCESS);
		vfs_set_feature(vfsp, VFSFT_ACLONCREATE);
	}
	if (zfsvfs->z_case == ZFS_CASE_INSENSITIVE) {
		vfs_set_feature(vfsp, VFSFT_DIRENTFLAGS);
		vfs_set_feature(vfsp, VFSFT_CASEINSENSITIVE);
		vfs_set_feature(vfsp, VFSFT_NOCASESENSITIVE);
	} else if (zfsvfs->z_case == ZFS_CASE_MIXED) {
		vfs_set_feature(vfsp, VFSFT_DIRENTFLAGS);
		vfs_set_feature(vfsp, VFSFT_CASEINSENSITIVE);
	}

	if (dmu_objset_is_snapshot(zfsvfs->z_os)) {
		uint64_t pval;

		ASSERT(mode & DS_MODE_READONLY);
		atime_changed_cb(zfsvfs, B_FALSE);
		readonly_changed_cb(zfsvfs, B_TRUE);
		if (error = dsl_prop_get_integer(osname, "xattr", &pval, NULL))
			goto out;
		xattr_changed_cb(zfsvfs, pval);
		zfsvfs->z_issnap = B_TRUE;
	} else {
		error = zfsvfs_setup(zfsvfs, B_TRUE);
	}

	if (!zfsvfs->z_issnap)
		zfsctl_create(zfsvfs);
out:
	if (error) {
		if (zfsvfs->z_os)
			dmu_objset_close(zfsvfs->z_os);
		zfs_freezfsvfs(zfsvfs);
	} else {
		atomic_add_32(&zfs_active_fs_count, 1);
	}

	return (error);
}

void
zfs_unregister_callbacks(zfsvfs_t *zfsvfs)
{
	objset_t *os = zfsvfs->z_os;
	struct dsl_dataset *ds;

	/*
	 * Unregister properties.
	 */
	if (!dmu_objset_is_snapshot(os)) {
		ds = dmu_objset_ds(os);
		VERIFY(dsl_prop_unregister(ds, "atime", atime_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "xattr", xattr_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "recordsize", blksz_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "readonly", readonly_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "devices", devices_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "setuid", setuid_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "exec", exec_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "snapdir", snapdir_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "aclmode", acl_mode_changed_cb,
		    zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "aclinherit",
		    acl_inherit_changed_cb, zfsvfs) == 0);

		VERIFY(dsl_prop_unregister(ds, "vscan",
		    vscan_changed_cb, zfsvfs) == 0);
	}
}

/*
 * Convert a decimal digit string to a uint64_t integer.
 */
static int
str_to_uint64(char *str, uint64_t *objnum)
{
	uint64_t num = 0;

	while (*str) {
		if (*str < '0' || *str > '9')
			return (EINVAL);

		num = num*10 + *str++ - '0';
	}

	*objnum = num;
	return (0);
}

/*
 * The boot path passed from the boot loader is in the form of
 * "rootpool-name/root-filesystem-object-number'. Convert this
 * string to a dataset name: "rootpool-name/root-filesystem-name".
 */
static int
zfs_parse_bootfs(char *bpath, char *outpath)
{
	char *slashp;
	uint64_t objnum;
	int error;

	if (*bpath == 0 || *bpath == '/')
		return (EINVAL);

	(void) strcpy(outpath, bpath);

	slashp = strchr(bpath, '/');

	/* if no '/', just return the pool name */
	if (slashp == NULL) {
		return (0);
	}

	/* if not a number, just return the root dataset name */
	if (str_to_uint64(slashp+1, &objnum)) {
		return (0);
	}

	*slashp = '\0';
	error = dsl_dsobj_to_dsname(bpath, objnum, outpath);
	*slashp = '/';

	return (error);
}

static int
zfs_mountroot(vfs_t *vfsp, enum whymountroot why)
{
	int error = 0;
	static int zfsrootdone = 0;
	zfsvfs_t *zfsvfs = NULL;
	znode_t *zp = NULL;
	vnode_t *vp = NULL;
	char *zfs_bootfs;
	char *zfs_devid;

	ASSERT(vfsp);

	/*
	 * The filesystem that we mount as root is defined in the
	 * boot property "zfs-bootfs" with a format of
	 * "poolname/root-dataset-objnum".
	 */
	if (why == ROOT_INIT) {
		if (zfsrootdone++)
			return (EBUSY);
		/*
		 * the process of doing a spa_load will require the
		 * clock to be set before we could (for example) do
		 * something better by looking at the timestamp on
		 * an uberblock, so just set it to -1.
		 */
		clkset(-1);

		if ((zfs_bootfs = spa_get_bootprop("zfs-bootfs")) == NULL) {
			cmn_err(CE_NOTE, "spa_get_bootfs: can not get "
			    "bootfs name");
			return (EINVAL);
		}
		zfs_devid = spa_get_bootprop("diskdevid");
		error = spa_import_rootpool(rootfs.bo_name, zfs_devid);
		if (zfs_devid)
			spa_free_bootprop(zfs_devid);
		if (error) {
			spa_free_bootprop(zfs_bootfs);
			cmn_err(CE_NOTE, "spa_import_rootpool: error %d",
			    error);
			return (error);
		}
		if (error = zfs_parse_bootfs(zfs_bootfs, rootfs.bo_name)) {
			spa_free_bootprop(zfs_bootfs);
			cmn_err(CE_NOTE, "zfs_parse_bootfs: error %d",
			    error);
			return (error);
		}

		spa_free_bootprop(zfs_bootfs);

		if (error = vfs_lock(vfsp))
			return (error);

		if (error = zfs_domount(vfsp, rootfs.bo_name)) {
			cmn_err(CE_NOTE, "zfs_domount: error %d", error);
			goto out;
		}

		zfsvfs = (zfsvfs_t *)vfsp->vfs_data;
		ASSERT(zfsvfs);
		if (error = zfs_zget(zfsvfs, zfsvfs->z_root, &zp)) {
			cmn_err(CE_NOTE, "zfs_zget: error %d", error);
			goto out;
		}

		vp = ZTOV(zp);
		mutex_enter(&vp->v_lock);
		vp->v_flag |= VROOT;
		mutex_exit(&vp->v_lock);
		rootvp = vp;

		/*
		 * Leave rootvp held.  The root file system is never unmounted.
		 */

		vfs_add((struct vnode *)0, vfsp,
		    (vfsp->vfs_flag & VFS_RDONLY) ? MS_RDONLY : 0);
out:
		vfs_unlock(vfsp);
		return (error);
	} else if (why == ROOT_REMOUNT) {
		readonly_changed_cb(vfsp->vfs_data, B_FALSE);
		vfsp->vfs_flag |= VFS_REMOUNT;

		/* refresh mount options */
		zfs_unregister_callbacks(vfsp->vfs_data);
		return (zfs_register_callbacks(vfsp));

	} else if (why == ROOT_UNMOUNT) {
		zfs_unregister_callbacks((zfsvfs_t *)vfsp->vfs_data);
		(void) zfs_sync(vfsp, 0, 0);
		return (0);
	}

	/*
	 * if "why" is equal to anything else other than ROOT_INIT,
	 * ROOT_REMOUNT, or ROOT_UNMOUNT, we do not support it.
	 */
	return (ENOTSUP);
}

/*ARGSUSED*/
static int
zfs_mount(vfs_t *vfsp, vnode_t *mvp, struct mounta *uap, cred_t *cr)
{
	char		*osname;
	pathname_t	spn;
	int		error = 0;
	uio_seg_t	fromspace = (uap->flags & MS_SYSSPACE) ?
	    UIO_SYSSPACE : UIO_USERSPACE;
	int		canwrite;

	if (mvp->v_type != VDIR)
		return (ENOTDIR);

	mutex_enter(&mvp->v_lock);
	if ((uap->flags & MS_REMOUNT) == 0 &&
	    (uap->flags & MS_OVERLAY) == 0 &&
	    (mvp->v_count != 1 || (mvp->v_flag & VROOT))) {
		mutex_exit(&mvp->v_lock);
		return (EBUSY);
	}
	mutex_exit(&mvp->v_lock);

	/*
	 * ZFS does not support passing unparsed data in via MS_DATA.
	 * Users should use the MS_OPTIONSTR interface; this means
	 * that all option parsing is already done and the options struct
	 * can be interrogated.
	 */
	if ((uap->flags & MS_DATA) && uap->datalen > 0)
		return (EINVAL);

	/*
	 * Get the objset name (the "special" mount argument).
	 */
	if (error = pn_get(uap->spec, fromspace, &spn))
		return (error);

	osname = spn.pn_path;

	/*
	 * Check for mount privilege?
	 *
	 * If we don't have privilege then see if
	 * we have local permission to allow it
	 */
	error = secpolicy_fs_mount(cr, mvp, vfsp);
	if (error) {
		error = dsl_deleg_access(osname, ZFS_DELEG_PERM_MOUNT, cr);
		if (error == 0) {
			vattr_t		vattr;

			/*
			 * Make sure user is the owner of the mount point
			 * or has sufficient privileges.
			 */

			vattr.va_mask = AT_UID;

			if (error = VOP_GETATTR(mvp, &vattr, 0, cr, NULL)) {
				goto out;
			}

			if (secpolicy_vnode_owner(cr, vattr.va_uid) != 0 &&
			    VOP_ACCESS(mvp, VWRITE, 0, cr, NULL) != 0) {
				error = EPERM;
				goto out;
			}

			secpolicy_fs_mount_clearopts(cr, vfsp);
		} else {
			goto out;
		}
	}

	/*
	 * Refuse to mount a filesystem if we are in a local zone and the
	 * dataset is not visible.
	 */
	if (!INGLOBALZONE(curproc) &&
	    (!zone_dataset_visible(osname, &canwrite) || !canwrite)) {
		error = EPERM;
		goto out;
	}

	/*
	 * When doing a remount, we simply refresh our temporary properties
	 * according to those options set in the current VFS options.
	 */
	if (uap->flags & MS_REMOUNT) {
		/* refresh mount options */
		zfs_unregister_callbacks(vfsp->vfs_data);
		error = zfs_register_callbacks(vfsp);
		goto out;
	}

	error = zfs_domount(vfsp, osname);

out:
	pn_free(&spn);
	return (error);
}

static int
zfs_statvfs(vfs_t *vfsp, struct statvfs64 *statp)
{
	zfsvfs_t *zfsvfs = vfsp->vfs_data;
	dev32_t d32;
	uint64_t refdbytes, availbytes, usedobjs, availobjs;

	ZFS_ENTER(zfsvfs);

	dmu_objset_space(zfsvfs->z_os,
	    &refdbytes, &availbytes, &usedobjs, &availobjs);

	/*
	 * The underlying storage pool actually uses multiple block sizes.
	 * We report the fragsize as the smallest block size we support,
	 * and we report our blocksize as the filesystem's maximum blocksize.
	 */
	statp->f_frsize = 1UL << SPA_MINBLOCKSHIFT;
	statp->f_bsize = zfsvfs->z_max_blksz;

	/*
	 * The following report "total" blocks of various kinds in the
	 * file system, but reported in terms of f_frsize - the
	 * "fragment" size.
	 */

	statp->f_blocks = (refdbytes + availbytes) >> SPA_MINBLOCKSHIFT;
	statp->f_bfree = availbytes >> SPA_MINBLOCKSHIFT;
	statp->f_bavail = statp->f_bfree; /* no root reservation */

	/*
	 * statvfs() should really be called statufs(), because it assumes
	 * static metadata.  ZFS doesn't preallocate files, so the best
	 * we can do is report the max that could possibly fit in f_files,
	 * and that minus the number actually used in f_ffree.
	 * For f_ffree, report the smaller of the number of object available
	 * and the number of blocks (each object will take at least a block).
	 */
	statp->f_ffree = MIN(availobjs, statp->f_bfree);
	statp->f_favail = statp->f_ffree;	/* no "root reservation" */
	statp->f_files = statp->f_ffree + usedobjs;

	(void) cmpldev(&d32, vfsp->vfs_dev);
	statp->f_fsid = d32;

	/*
	 * We're a zfs filesystem.
	 */
	(void) strcpy(statp->f_basetype, vfssw[vfsp->vfs_fstype].vsw_name);

	statp->f_flag = vf_to_stf(vfsp->vfs_flag);

	statp->f_namemax = ZFS_MAXNAMELEN;

	/*
	 * We have all of 32 characters to stuff a string here.
	 * Is there anything useful we could/should provide?
	 */
	bzero(statp->f_fstr, sizeof (statp->f_fstr));

	ZFS_EXIT(zfsvfs);
	return (0);
}

static int
zfs_root(vfs_t *vfsp, vnode_t **vpp)
{
	zfsvfs_t *zfsvfs = vfsp->vfs_data;
	znode_t *rootzp;
	int error;

	ZFS_ENTER(zfsvfs);

	error = zfs_zget(zfsvfs, zfsvfs->z_root, &rootzp);
	if (error == 0)
		*vpp = ZTOV(rootzp);

	ZFS_EXIT(zfsvfs);
	return (error);
}

/*
 * Teardown the zfsvfs::z_os.
 *
 * Note, if 'unmounting' if FALSE, we return with the 'z_teardown_lock'
 * and 'z_teardown_inactive_lock' held.
 */
static int
zfsvfs_teardown(zfsvfs_t *zfsvfs, boolean_t unmounting)
{
	znode_t	*zp;

	rrw_enter(&zfsvfs->z_teardown_lock, RW_WRITER, FTAG);

	if (!unmounting) {
		/*
		 * We purge the parent filesystem's vfsp as the parent
		 * filesystem and all of its snapshots have their vnode's
		 * v_vfsp set to the parent's filesystem's vfsp.  Note,
		 * 'z_parent' is self referential for non-snapshots.
		 */
		(void) dnlc_purge_vfsp(zfsvfs->z_parent->z_vfs, 0);
	}

	/*
	 * Close the zil. NB: Can't close the zil while zfs_inactive
	 * threads are blocked as zil_close can call zfs_inactive.
	 */
	if (zfsvfs->z_log) {
		zil_close(zfsvfs->z_log);
		zfsvfs->z_log = NULL;
	}

	rw_enter(&zfsvfs->z_teardown_inactive_lock, RW_WRITER);

	/*
	 * If we are not unmounting (ie: online recv) and someone already
	 * unmounted this file system while we were doing the switcheroo,
	 * or a reopen of z_os failed then just bail out now.
	 */
	if (!unmounting && (zfsvfs->z_unmounted || zfsvfs->z_os == NULL)) {
		rw_exit(&zfsvfs->z_teardown_inactive_lock);
		rrw_exit(&zfsvfs->z_teardown_lock, FTAG);
		return (EIO);
	}

	/*
	 * At this point there are no vops active, and any new vops will
	 * fail with EIO since we have z_teardown_lock for writer (only
	 * relavent for forced unmount).
	 *
	 * Release all holds on dbufs.
	 */
	mutex_enter(&zfsvfs->z_znodes_lock);
	for (zp = list_head(&zfsvfs->z_all_znodes); zp != NULL;
	    zp = list_next(&zfsvfs->z_all_znodes, zp))
		if (zp->z_dbuf) {
			ASSERT(ZTOV(zp)->v_count > 0);
			zfs_znode_dmu_fini(zp);
		}
	mutex_exit(&zfsvfs->z_znodes_lock);

	/*
	 * If we are unmounting, set the unmounted flag and let new vops
	 * unblock.  zfs_inactive will have the unmounted behavior, and all
	 * other vops will fail with EIO.
	 */
	if (unmounting) {
		zfsvfs->z_unmounted = B_TRUE;
		rrw_exit(&zfsvfs->z_teardown_lock, FTAG);
		rw_exit(&zfsvfs->z_teardown_inactive_lock);
	}

	/*
	 * z_os will be NULL if there was an error in attempting to reopen
	 * zfsvfs, so just return as the properties had already been
	 * unregistered and cached data had been evicted before.
	 */
	if (zfsvfs->z_os == NULL)
		return (0);

	/*
	 * Unregister properties.
	 */
	zfs_unregister_callbacks(zfsvfs);

	/*
	 * Evict cached data
	 */
	if (dmu_objset_evict_dbufs(zfsvfs->z_os)) {
		txg_wait_synced(dmu_objset_pool(zfsvfs->z_os), 0);
		(void) dmu_objset_evict_dbufs(zfsvfs->z_os);
	}

	return (0);
}

/*ARGSUSED*/
static int
zfs_umount(vfs_t *vfsp, int fflag, cred_t *cr)
{
	zfsvfs_t *zfsvfs = vfsp->vfs_data;
	objset_t *os;
	int ret;

	ret = secpolicy_fs_unmount(cr, vfsp);
	if (ret) {
		ret = dsl_deleg_access((char *)refstr_value(vfsp->vfs_resource),
		    ZFS_DELEG_PERM_MOUNT, cr);
		if (ret)
			return (ret);
	}

	/*
	 * We purge the parent filesystem's vfsp as the parent filesystem
	 * and all of its snapshots have their vnode's v_vfsp set to the
	 * parent's filesystem's vfsp.  Note, 'z_parent' is self
	 * referential for non-snapshots.
	 */
	(void) dnlc_purge_vfsp(zfsvfs->z_parent->z_vfs, 0);

	/*
	 * Unmount any snapshots mounted under .zfs before unmounting the
	 * dataset itself.
	 */
	if (zfsvfs->z_ctldir != NULL &&
	    (ret = zfsctl_umount_snapshots(vfsp, fflag, cr)) != 0) {
		return (ret);
	}

	if (!(fflag & MS_FORCE)) {
		/*
		 * Check the number of active vnodes in the file system.
		 * Our count is maintained in the vfs structure, but the
		 * number is off by 1 to indicate a hold on the vfs
		 * structure itself.
		 *
		 * The '.zfs' directory maintains a reference of its
		 * own, and any active references underneath are
		 * reflected in the vnode count.
		 */
		if (zfsvfs->z_ctldir == NULL) {
			if (vfsp->vfs_count > 1)
				return (EBUSY);
		} else {
			if (vfsp->vfs_count > 2 ||
			    zfsvfs->z_ctldir->v_count > 1)
				return (EBUSY);
		}
	}

	vfsp->vfs_flag |= VFS_UNMOUNTED;

	VERIFY(zfsvfs_teardown(zfsvfs, B_TRUE) == 0);
	os = zfsvfs->z_os;

	/*
	 * z_os will be NULL if there was an error in
	 * attempting to reopen zfsvfs.
	 */
	if (os != NULL) {
		/*
		 * Unset the objset user_ptr.
		 */
		mutex_enter(&os->os->os_user_ptr_lock);
		dmu_objset_set_user(os, NULL);
		mutex_exit(&os->os->os_user_ptr_lock);

		/*
		 * Finally release the objset
		 */
		dmu_objset_close(os);
	}

	/*
	 * We can now safely destroy the '.zfs' directory node.
	 */
	if (zfsvfs->z_ctldir != NULL)
		zfsctl_destroy(zfsvfs);

	return (0);
}

static int
zfs_vget(vfs_t *vfsp, vnode_t **vpp, fid_t *fidp)
{
	zfsvfs_t	*zfsvfs = vfsp->vfs_data;
	znode_t		*zp;
	uint64_t	object = 0;
	uint64_t	fid_gen = 0;
	uint64_t	gen_mask;
	uint64_t	zp_gen;
	int 		i, err;

	*vpp = NULL;

	ZFS_ENTER(zfsvfs);

	if (fidp->fid_len == LONG_FID_LEN) {
		zfid_long_t	*zlfid = (zfid_long_t *)fidp;
		uint64_t	objsetid = 0;
		uint64_t	setgen = 0;

		for (i = 0; i < sizeof (zlfid->zf_setid); i++)
			objsetid |= ((uint64_t)zlfid->zf_setid[i]) << (8 * i);

		for (i = 0; i < sizeof (zlfid->zf_setgen); i++)
			setgen |= ((uint64_t)zlfid->zf_setgen[i]) << (8 * i);

		ZFS_EXIT(zfsvfs);

		err = zfsctl_lookup_objset(vfsp, objsetid, &zfsvfs);
		if (err)
			return (EINVAL);
		ZFS_ENTER(zfsvfs);
	}

	if (fidp->fid_len == SHORT_FID_LEN || fidp->fid_len == LONG_FID_LEN) {
		zfid_short_t	*zfid = (zfid_short_t *)fidp;

		for (i = 0; i < sizeof (zfid->zf_object); i++)
			object |= ((uint64_t)zfid->zf_object[i]) << (8 * i);

		for (i = 0; i < sizeof (zfid->zf_gen); i++)
			fid_gen |= ((uint64_t)zfid->zf_gen[i]) << (8 * i);
	} else {
		ZFS_EXIT(zfsvfs);
		return (EINVAL);
	}

	/* A zero fid_gen means we are in the .zfs control directories */
	if (fid_gen == 0 &&
	    (object == ZFSCTL_INO_ROOT || object == ZFSCTL_INO_SNAPDIR)) {
		*vpp = zfsvfs->z_ctldir;
		ASSERT(*vpp != NULL);
		if (object == ZFSCTL_INO_SNAPDIR) {
			VERIFY(zfsctl_root_lookup(*vpp, "snapshot", vpp, NULL,
			    0, NULL, NULL, NULL, NULL, NULL) == 0);
		} else {
			VN_HOLD(*vpp);
		}
		ZFS_EXIT(zfsvfs);
		return (0);
	}

	gen_mask = -1ULL >> (64 - 8 * i);

	dprintf("getting %llu [%u mask %llx]\n", object, fid_gen, gen_mask);
	if (err = zfs_zget(zfsvfs, object, &zp)) {
		ZFS_EXIT(zfsvfs);
		return (err);
	}
	zp_gen = zp->z_phys->zp_gen & gen_mask;
	if (zp_gen == 0)
		zp_gen = 1;
	if (zp->z_unlinked || zp_gen != fid_gen) {
		dprintf("znode gen (%u) != fid gen (%u)\n", zp_gen, fid_gen);
		VN_RELE(ZTOV(zp));
		ZFS_EXIT(zfsvfs);
		return (EINVAL);
	}

	*vpp = ZTOV(zp);
	ZFS_EXIT(zfsvfs);
	return (0);
}

/*
 * Block out VOPs and close zfsvfs_t::z_os
 *
 * Note, if successful, then we return with the 'z_teardown_lock' and
 * 'z_teardown_inactive_lock' write held.
 */
int
zfs_suspend_fs(zfsvfs_t *zfsvfs, char *name, int *mode)
{
	int error;

	if ((error = zfsvfs_teardown(zfsvfs, B_FALSE)) != 0)
		return (error);

	*mode = zfsvfs->z_os->os_mode;
	dmu_objset_name(zfsvfs->z_os, name);
	dmu_objset_close(zfsvfs->z_os);

	return (0);
}

/*
 * Reopen zfsvfs_t::z_os and release VOPs.
 */
int
zfs_resume_fs(zfsvfs_t *zfsvfs, const char *osname, int mode)
{
	int err;

	ASSERT(RRW_WRITE_HELD(&zfsvfs->z_teardown_lock));
	ASSERT(RW_WRITE_HELD(&zfsvfs->z_teardown_inactive_lock));

	err = dmu_objset_open(osname, DMU_OST_ZFS, mode, &zfsvfs->z_os);
	if (err) {
		zfsvfs->z_os = NULL;
	} else {
		znode_t *zp;

		VERIFY(zfsvfs_setup(zfsvfs, B_FALSE) == 0);

		/*
		 * Attempt to re-establish all the active znodes with
		 * their dbufs.  If a zfs_rezget() fails, then we'll let
		 * any potential callers discover that via ZFS_ENTER_VERIFY_VP
		 * when they try to use their znode.
		 */
		mutex_enter(&zfsvfs->z_znodes_lock);
		for (zp = list_head(&zfsvfs->z_all_znodes); zp;
		    zp = list_next(&zfsvfs->z_all_znodes, zp)) {
			(void) zfs_rezget(zp);
		}
		mutex_exit(&zfsvfs->z_znodes_lock);

	}

	/* release the VOPs */
	rw_exit(&zfsvfs->z_teardown_inactive_lock);
	rrw_exit(&zfsvfs->z_teardown_lock, FTAG);

	if (err) {
		/*
		 * Since we couldn't reopen zfsvfs::z_os, force
		 * unmount this file system.
		 */
		if (vn_vfswlock(zfsvfs->z_vfs->vfs_vnodecovered) == 0)
			(void) dounmount(zfsvfs->z_vfs, MS_FORCE, CRED());
	}
	return (err);
}

static void
zfs_freevfs(vfs_t *vfsp)
{
	zfsvfs_t *zfsvfs = vfsp->vfs_data;
	int i;

	for (i = 0; i != ZFS_OBJ_MTX_SZ; i++)
		mutex_destroy(&zfsvfs->z_hold_mtx[i]);

	zfs_fuid_destroy(zfsvfs);
	zfs_freezfsvfs(zfsvfs);

	atomic_add_32(&zfs_active_fs_count, -1);
}

/*
 * VFS_INIT() initialization.  Note that there is no VFS_FINI(),
 * so we can't safely do any non-idempotent initialization here.
 * Leave that to zfs_init() and zfs_fini(), which are called
 * from the module's _init() and _fini() entry points.
 */
/*ARGSUSED*/
static int
zfs_vfsinit(int fstype, char *name)
{
	int error;

	zfsfstype = fstype;

	/*
	 * Setup vfsops and vnodeops tables.
	 */
	error = vfs_setfsops(fstype, zfs_vfsops_template, &zfs_vfsops);
	if (error != 0) {
		cmn_err(CE_WARN, "zfs: bad vfs ops template");
	}

	error = zfs_create_op_tables();
	if (error) {
		zfs_remove_op_tables();
		cmn_err(CE_WARN, "zfs: bad vnode ops template");
		(void) vfs_freevfsops_by_type(zfsfstype);
		return (error);
	}

	mutex_init(&zfs_dev_mtx, NULL, MUTEX_DEFAULT, NULL);

	/*
	 * Unique major number for all zfs mounts.
	 * If we run out of 32-bit minors, we'll getudev() another major.
	 */
	zfs_major = ddi_name_to_major(ZFS_DRIVER);
	zfs_minor = ZFS_MIN_MINOR;

	return (0);
}

void
zfs_init(void)
{
	/*
	 * Initialize .zfs directory structures
	 */
	zfsctl_init();

	/*
	 * Initialize znode cache, vnode ops, etc...
	 */
	zfs_znode_init();
}

void
zfs_fini(void)
{
	zfsctl_fini();
	zfs_znode_fini();
}

int
zfs_busy(void)
{
	return (zfs_active_fs_count != 0);
}

int
zfs_set_version(const char *name, uint64_t newvers)
{
	int error;
	objset_t *os;
	dmu_tx_t *tx;
	uint64_t curvers;

	/*
	 * XXX for now, require that the filesystem be unmounted.  Would
	 * be nice to find the zfsvfs_t and just update that if
	 * possible.
	 */

	if (newvers < ZPL_VERSION_INITIAL || newvers > ZPL_VERSION)
		return (EINVAL);

	error = dmu_objset_open(name, DMU_OST_ZFS, DS_MODE_OWNER, &os);
	if (error)
		return (error);

	error = zap_lookup(os, MASTER_NODE_OBJ, ZPL_VERSION_STR,
	    8, 1, &curvers);
	if (error)
		goto out;
	if (newvers < curvers) {
		error = EINVAL;
		goto out;
	}

	tx = dmu_tx_create(os);
	dmu_tx_hold_zap(tx, MASTER_NODE_OBJ, 0, ZPL_VERSION_STR);
	error = dmu_tx_assign(tx, TXG_WAIT);
	if (error) {
		dmu_tx_abort(tx);
		goto out;
	}
	error = zap_update(os, MASTER_NODE_OBJ, ZPL_VERSION_STR, 8, 1,
	    &newvers, tx);

	spa_history_internal_log(LOG_DS_UPGRADE,
	    dmu_objset_spa(os), tx, CRED(),
	    "oldver=%llu newver=%llu dataset = %llu", curvers, newvers,
	    dmu_objset_id(os));
	dmu_tx_commit(tx);

out:
	dmu_objset_close(os);
	return (error);
}

/*
 * Read a property stored within the master node.
 */
int
zfs_get_zplprop(objset_t *os, zfs_prop_t prop, uint64_t *value)
{
	const char *pname;
	int error = ENOENT;

	/*
	 * Look up the file system's value for the property.  For the
	 * version property, we look up a slightly different string.
	 */
	if (prop == ZFS_PROP_VERSION)
		pname = ZPL_VERSION_STR;
	else
		pname = zfs_prop_to_name(prop);

	if (os != NULL)
		error = zap_lookup(os, MASTER_NODE_OBJ, pname, 8, 1, value);

	if (error == ENOENT) {
		/* No value set, use the default value */
		switch (prop) {
		case ZFS_PROP_VERSION:
			*value = ZPL_VERSION;
			break;
		case ZFS_PROP_NORMALIZE:
		case ZFS_PROP_UTF8ONLY:
			*value = 0;
			break;
		case ZFS_PROP_CASE:
			*value = ZFS_CASE_SENSITIVE;
			break;
		default:
			return (error);
		}
		error = 0;
	}
	return (error);
}

static vfsdef_t vfw = {
	VFSDEF_VERSION,
	MNTTYPE_ZFS,
	zfs_vfsinit,
	VSW_HASPROTO|VSW_CANRWRO|VSW_CANREMOUNT|VSW_VOLATILEDEV|VSW_STATS|
	    VSW_XID,
	&zfs_mntopts
};

struct modlfs zfs_modlfs = {
	&mod_fsops, "ZFS filesystem version " SPA_VERSION_STRING, &vfw
};