Fix false assertion in dmu_tx_dirty_buf() on cloning

[zfs.git] / lib / libzfs / libzfs_changelist.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 https://opensource.org/licenses/CDDL-1.0.
 * 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 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * Portions Copyright 2007 Ramprakash Jelari
 * Copyright (c) 2014, 2020 by Delphix. All rights reserved.
 * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
 * Copyright (c) 2018 Datto Inc.
 */

#include <libintl.h>
#include <libuutil.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <zone.h>

#include <libzfs.h>

#include "libzfs_impl.h"

/*
 * Structure to keep track of dataset state.  Before changing the 'sharenfs' or
 * 'mountpoint' property, we record whether the filesystem was previously
 * mounted/shared.  This prior state dictates whether we remount/reshare the
 * dataset after the property has been changed.
 *
 * The interface consists of the following sequence of functions:
 *
 *      changelist_gather()
 *      changelist_prefix()
 *      < change property >
 *      changelist_postfix()
 *      changelist_free()
 *
 * Other interfaces:
 *
 * changelist_remove() - remove a node from a gathered list
 * changelist_rename() - renames all datasets appropriately when doing a rename
 * changelist_unshare() - unshares all the nodes in a given changelist
 * changelist_haszonedchild() - check if there is any child exported to
 *                              a local zone
 */
typedef struct prop_changenode {
        zfs_handle_t            *cn_handle;
        int                     cn_shared;
        int                     cn_mounted;
        int                     cn_zoned;
        boolean_t               cn_needpost;    /* is postfix() needed? */
        uu_avl_node_t           cn_treenode;
} prop_changenode_t;

struct prop_changelist {
        zfs_prop_t              cl_prop;
        zfs_prop_t              cl_realprop;
        zfs_prop_t              cl_shareprop;  /* used with sharenfs/sharesmb */
        uu_avl_pool_t           *cl_pool;
        uu_avl_t                *cl_tree;
        boolean_t               cl_waslegacy;
        boolean_t               cl_allchildren;
        boolean_t               cl_alldependents;
        int                     cl_mflags;      /* Mount flags */
        int                     cl_gflags;      /* Gather request flags */
        boolean_t               cl_haszonedchild;
};

/*
 * If the property is 'mountpoint', go through and unmount filesystems as
 * necessary.  We don't do the same for 'sharenfs', because we can just re-share
 * with different options without interrupting service. We do handle 'sharesmb'
 * since there may be old resource names that need to be removed.
 */
int
changelist_prefix(prop_changelist_t *clp)
{
        prop_changenode_t *cn;
        uu_avl_walk_t *walk;
        int ret = 0;
        const enum sa_protocol smb[] = {SA_PROTOCOL_SMB, SA_NO_PROTOCOL};
        boolean_t commit_smb_shares = B_FALSE;

        if (clp->cl_prop != ZFS_PROP_MOUNTPOINT &&
            clp->cl_prop != ZFS_PROP_SHARESMB)
                return (0);

        /*
         * If CL_GATHER_DONT_UNMOUNT is set, don't want to unmount/unshare and
         * later (re)mount/(re)share the filesystem in postfix phase, so we
         * return from here. If filesystem is mounted or unmounted, leave it
         * as it is.
         */
        if (clp->cl_gflags & CL_GATHER_DONT_UNMOUNT)
                return (0);

        if ((walk = uu_avl_walk_start(clp->cl_tree, UU_WALK_ROBUST)) == NULL)
                return (-1);

        while ((cn = uu_avl_walk_next(walk)) != NULL) {

                /* if a previous loop failed, set the remaining to false */
                if (ret == -1) {
                        cn->cn_needpost = B_FALSE;
                        continue;
                }

                /*
                 * If we are in the global zone, but this dataset is exported
                 * to a local zone, do nothing.
                 */
                if (getzoneid() == GLOBAL_ZONEID && cn->cn_zoned)
                        continue;

                if (!ZFS_IS_VOLUME(cn->cn_handle)) {
                        /*
                         * Do the property specific processing.
                         */
                        switch (clp->cl_prop) {
                        case ZFS_PROP_MOUNTPOINT:
                                if (zfs_unmount(cn->cn_handle, NULL,
                                    clp->cl_mflags) != 0) {
                                        ret = -1;
                                        cn->cn_needpost = B_FALSE;
                                }
                                break;
                        case ZFS_PROP_SHARESMB:
                                (void) zfs_unshare(cn->cn_handle, NULL,
                                    smb);
                                commit_smb_shares = B_TRUE;
                                break;

                        default:
                                break;
                        }
                }
        }

        if (commit_smb_shares)
                zfs_commit_shares(smb);
        uu_avl_walk_end(walk);

        if (ret == -1)
                (void) changelist_postfix(clp);

        return (ret);
}

/*
 * If the property is 'mountpoint' or 'sharenfs', go through and remount and/or
 * reshare the filesystems as necessary.  In changelist_gather() we recorded
 * whether the filesystem was previously shared or mounted.  The action we take
 * depends on the previous state, and whether the value was previously 'legacy'.
 * For non-legacy properties, we always remount/reshare the filesystem,
 * if CL_GATHER_DONT_UNMOUNT is not set.
 */
int
changelist_postfix(prop_changelist_t *clp)
{
        prop_changenode_t *cn;
        uu_avl_walk_t *walk;
        char shareopts[ZFS_MAXPROPLEN];
        boolean_t commit_smb_shares = B_FALSE;
        boolean_t commit_nfs_shares = B_FALSE;

        /*
         * If CL_GATHER_DONT_UNMOUNT is set, it means we don't want to (un)mount
         * or (re/un)share the filesystem, so we return from here. If filesystem
         * is mounted or unmounted, leave it as it is.
         */
        if (clp->cl_gflags & CL_GATHER_DONT_UNMOUNT)
                return (0);

        /*
         * If we're changing the mountpoint, attempt to destroy the underlying
         * mountpoint.  All other datasets will have inherited from this dataset
         * (in which case their mountpoints exist in the filesystem in the new
         * location), or have explicit mountpoints set (in which case they won't
         * be in the changelist).
         */
        if ((cn = uu_avl_last(clp->cl_tree)) == NULL)
                return (0);

        if (clp->cl_prop == ZFS_PROP_MOUNTPOINT &&
            !(clp->cl_gflags & CL_GATHER_DONT_UNMOUNT))
                remove_mountpoint(cn->cn_handle);

        /*
         * We walk the datasets in reverse, because we want to mount any parent
         * datasets before mounting the children.  We walk all datasets even if
         * there are errors.
         */
        if ((walk = uu_avl_walk_start(clp->cl_tree,
            UU_WALK_REVERSE | UU_WALK_ROBUST)) == NULL)
                return (-1);

        while ((cn = uu_avl_walk_next(walk)) != NULL) {

                boolean_t sharenfs;
                boolean_t sharesmb;
                boolean_t mounted;
                boolean_t needs_key;

                /*
                 * If we are in the global zone, but this dataset is exported
                 * to a local zone, do nothing.
                 */
                if (getzoneid() == GLOBAL_ZONEID && cn->cn_zoned)
                        continue;

                /* Only do post-processing if it's required */
                if (!cn->cn_needpost)
                        continue;
                cn->cn_needpost = B_FALSE;

                zfs_refresh_properties(cn->cn_handle);

                if (ZFS_IS_VOLUME(cn->cn_handle))
                        continue;

                /*
                 * Remount if previously mounted or mountpoint was legacy,
                 * or sharenfs or sharesmb  property is set.
                 */
                sharenfs = ((zfs_prop_get(cn->cn_handle, ZFS_PROP_SHARENFS,
                    shareopts, sizeof (shareopts), NULL, NULL, 0,
                    B_FALSE) == 0) && (strcmp(shareopts, "off") != 0));

                sharesmb = ((zfs_prop_get(cn->cn_handle, ZFS_PROP_SHARESMB,
                    shareopts, sizeof (shareopts), NULL, NULL, 0,
                    B_FALSE) == 0) && (strcmp(shareopts, "off") != 0));

                needs_key = (zfs_prop_get_int(cn->cn_handle,
                    ZFS_PROP_KEYSTATUS) == ZFS_KEYSTATUS_UNAVAILABLE);

                mounted = zfs_is_mounted(cn->cn_handle, NULL);

                if (!mounted && !needs_key && (cn->cn_mounted ||
                    (((clp->cl_prop == ZFS_PROP_MOUNTPOINT &&
                    clp->cl_prop == clp->cl_realprop) ||
                    sharenfs || sharesmb || clp->cl_waslegacy) &&
                    (zfs_prop_get_int(cn->cn_handle,
                    ZFS_PROP_CANMOUNT) == ZFS_CANMOUNT_ON)))) {

                        if (zfs_mount(cn->cn_handle, NULL, 0) == 0)
                                mounted = TRUE;
                }

                /*
                 * If the file system is mounted we always re-share even
                 * if the filesystem is currently shared, so that we can
                 * adopt any new options.
                 */
                const enum sa_protocol nfs[] =
                    {SA_PROTOCOL_NFS, SA_NO_PROTOCOL};
                if (sharenfs && mounted) {
                        zfs_share(cn->cn_handle, nfs);
                        commit_nfs_shares = B_TRUE;
                } else if (cn->cn_shared || clp->cl_waslegacy) {
                        zfs_unshare(cn->cn_handle, NULL, nfs);
                        commit_nfs_shares = B_TRUE;
                }
                const enum sa_protocol smb[] =
                    {SA_PROTOCOL_SMB, SA_NO_PROTOCOL};
                if (sharesmb && mounted) {
                        zfs_share(cn->cn_handle, smb);
                        commit_smb_shares = B_TRUE;
                } else if (cn->cn_shared || clp->cl_waslegacy) {
                        zfs_unshare(cn->cn_handle, NULL, smb);
                        commit_smb_shares = B_TRUE;
                }
        }

        enum sa_protocol proto[SA_PROTOCOL_COUNT + 1], *p = proto;
        if (commit_nfs_shares)
                *p++ = SA_PROTOCOL_NFS;
        if (commit_smb_shares)
                *p++ = SA_PROTOCOL_SMB;
        *p++ = SA_NO_PROTOCOL;
        zfs_commit_shares(proto);
        uu_avl_walk_end(walk);

        return (0);
}

/*
 * Is this "dataset" a child of "parent"?
 */
static boolean_t
isa_child_of(const char *dataset, const char *parent)
{
        int len;

        len = strlen(parent);

        if (strncmp(dataset, parent, len) == 0 &&
            (dataset[len] == '@' || dataset[len] == '/' ||
            dataset[len] == '\0'))
                return (B_TRUE);
        else
                return (B_FALSE);

}

/*
 * If we rename a filesystem, child filesystem handles are no longer valid
 * since we identify each dataset by its name in the ZFS namespace.  As a
 * result, we have to go through and fix up all the names appropriately.  We
 * could do this automatically if libzfs kept track of all open handles, but
 * this is a lot less work.
 */
void
changelist_rename(prop_changelist_t *clp, const char *src, const char *dst)
{
        prop_changenode_t *cn;
        uu_avl_walk_t *walk;
        char newname[ZFS_MAX_DATASET_NAME_LEN];

        if ((walk = uu_avl_walk_start(clp->cl_tree, UU_WALK_ROBUST)) == NULL)
                return;

        while ((cn = uu_avl_walk_next(walk)) != NULL) {
                /*
                 * Do not rename a clone that's not in the source hierarchy.
                 */
                if (!isa_child_of(cn->cn_handle->zfs_name, src))
                        continue;

                /*
                 * Destroy the previous mountpoint if needed.
                 */
                remove_mountpoint(cn->cn_handle);

                (void) strlcpy(newname, dst, sizeof (newname));
                (void) strlcat(newname, cn->cn_handle->zfs_name + strlen(src),
                    sizeof (newname));

                (void) strlcpy(cn->cn_handle->zfs_name, newname,
                    sizeof (cn->cn_handle->zfs_name));
        }

        uu_avl_walk_end(walk);
}

/*
 * Given a gathered changelist for the 'sharenfs' or 'sharesmb' property,
 * unshare all the datasets in the list.
 */
int
changelist_unshare(prop_changelist_t *clp, const enum sa_protocol *proto)
{
        prop_changenode_t *cn;
        uu_avl_walk_t *walk;
        int ret = 0;

        if (clp->cl_prop != ZFS_PROP_SHARENFS &&
            clp->cl_prop != ZFS_PROP_SHARESMB)
                return (0);

        if ((walk = uu_avl_walk_start(clp->cl_tree, UU_WALK_ROBUST)) == NULL)
                return (-1);

        while ((cn = uu_avl_walk_next(walk)) != NULL) {
                if (zfs_unshare(cn->cn_handle, NULL, proto) != 0)
                        ret = -1;
        }

        for (const enum sa_protocol *p = proto; *p != SA_NO_PROTOCOL; ++p)
                sa_commit_shares(*p);
        uu_avl_walk_end(walk);

        return (ret);
}

/*
 * Check if there is any child exported to a local zone in a given changelist.
 * This information has already been recorded while gathering the changelist
 * via changelist_gather().
 */
int
changelist_haszonedchild(prop_changelist_t *clp)
{
        return (clp->cl_haszonedchild);
}

/*
 * Remove a node from a gathered list.
 */
void
changelist_remove(prop_changelist_t *clp, const char *name)
{
        prop_changenode_t *cn;
        uu_avl_walk_t *walk;

        if ((walk = uu_avl_walk_start(clp->cl_tree, UU_WALK_ROBUST)) == NULL)
                return;

        while ((cn = uu_avl_walk_next(walk)) != NULL) {
                if (strcmp(cn->cn_handle->zfs_name, name) == 0) {
                        uu_avl_remove(clp->cl_tree, cn);
                        zfs_close(cn->cn_handle);
                        free(cn);
                        uu_avl_walk_end(walk);
                        return;
                }
        }

        uu_avl_walk_end(walk);
}

/*
 * Release any memory associated with a changelist.
 */
void
changelist_free(prop_changelist_t *clp)
{
        prop_changenode_t *cn;

        if (clp->cl_tree) {
                uu_avl_walk_t *walk;

                if ((walk = uu_avl_walk_start(clp->cl_tree,
                    UU_WALK_ROBUST)) == NULL)
                        return;

                while ((cn = uu_avl_walk_next(walk)) != NULL) {
                        uu_avl_remove(clp->cl_tree, cn);
                        zfs_close(cn->cn_handle);
                        free(cn);
                }

                uu_avl_walk_end(walk);
                uu_avl_destroy(clp->cl_tree);
        }
        if (clp->cl_pool)
                uu_avl_pool_destroy(clp->cl_pool);

        free(clp);
}

/*
 * Add one dataset to changelist
 */
static int
changelist_add_mounted(zfs_handle_t *zhp, void *data)
{
        prop_changelist_t *clp = data;
        prop_changenode_t *cn;
        uu_avl_index_t idx;

        ASSERT3U(clp->cl_prop, ==, ZFS_PROP_MOUNTPOINT);

        cn = zfs_alloc(zfs_get_handle(zhp), sizeof (prop_changenode_t));
        cn->cn_handle = zhp;
        cn->cn_mounted = zfs_is_mounted(zhp, NULL);
        ASSERT3U(cn->cn_mounted, ==, B_TRUE);
        cn->cn_shared = zfs_is_shared(zhp, NULL, NULL);
        cn->cn_zoned = zfs_prop_get_int(zhp, ZFS_PROP_ZONED);
        cn->cn_needpost = B_TRUE;

        /* Indicate if any child is exported to a local zone. */
        if (getzoneid() == GLOBAL_ZONEID && cn->cn_zoned)
                clp->cl_haszonedchild = B_TRUE;

        uu_avl_node_init(cn, &cn->cn_treenode, clp->cl_pool);

        if (uu_avl_find(clp->cl_tree, cn, NULL, &idx) == NULL) {
                uu_avl_insert(clp->cl_tree, cn, idx);
        } else {
                free(cn);
                zfs_close(zhp);
        }

        return (0);
}

static int
change_one(zfs_handle_t *zhp, void *data)
{
        prop_changelist_t *clp = data;
        char property[ZFS_MAXPROPLEN];
        char where[64];
        prop_changenode_t *cn = NULL;
        zprop_source_t sourcetype = ZPROP_SRC_NONE;
        zprop_source_t share_sourcetype = ZPROP_SRC_NONE;
        int ret = 0;

        /*
         * We only want to unmount/unshare those filesystems that may inherit
         * from the target filesystem.  If we find any filesystem with a
         * locally set mountpoint, we ignore any children since changing the
         * property will not affect them.  If this is a rename, we iterate
         * over all children regardless, since we need them unmounted in
         * order to do the rename.  Also, if this is a volume and we're doing
         * a rename, then always add it to the changelist.
         */

        if (!(ZFS_IS_VOLUME(zhp) && clp->cl_realprop == ZFS_PROP_NAME) &&
            zfs_prop_get(zhp, clp->cl_prop, property,
            sizeof (property), &sourcetype, where, sizeof (where),
            B_FALSE) != 0) {
                goto out;
        }

        /*
         * If we are "watching" sharenfs or sharesmb
         * then check out the companion property which is tracked
         * in cl_shareprop
         */
        if (clp->cl_shareprop != ZPROP_INVAL &&
            zfs_prop_get(zhp, clp->cl_shareprop, property,
            sizeof (property), &share_sourcetype, where, sizeof (where),
            B_FALSE) != 0) {
                goto out;
        }

        if (clp->cl_alldependents || clp->cl_allchildren ||
            sourcetype == ZPROP_SRC_DEFAULT ||
            sourcetype == ZPROP_SRC_INHERITED ||
            (clp->cl_shareprop != ZPROP_INVAL &&
            (share_sourcetype == ZPROP_SRC_DEFAULT ||
            share_sourcetype == ZPROP_SRC_INHERITED))) {
                cn = zfs_alloc(zfs_get_handle(zhp), sizeof (prop_changenode_t));
                cn->cn_handle = zhp;
                cn->cn_mounted = (clp->cl_gflags & CL_GATHER_MOUNT_ALWAYS) ||
                    zfs_is_mounted(zhp, NULL);
                cn->cn_shared = zfs_is_shared(zhp, NULL, NULL);
                cn->cn_zoned = zfs_prop_get_int(zhp, ZFS_PROP_ZONED);
                cn->cn_needpost = B_TRUE;

                /* Indicate if any child is exported to a local zone. */
                if (getzoneid() == GLOBAL_ZONEID && cn->cn_zoned)
                        clp->cl_haszonedchild = B_TRUE;

                uu_avl_node_init(cn, &cn->cn_treenode, clp->cl_pool);

                uu_avl_index_t idx;

                if (uu_avl_find(clp->cl_tree, cn, NULL, &idx) == NULL) {
                        uu_avl_insert(clp->cl_tree, cn, idx);
                } else {
                        free(cn);
                        cn = NULL;
                }

                if (!clp->cl_alldependents)
                        ret = zfs_iter_children_v2(zhp, 0, change_one, data);

                /*
                 * If we added the handle to the changelist, we will re-use it
                 * later so return without closing it.
                 */
                if (cn != NULL)
                        return (ret);
        }

out:
        zfs_close(zhp);
        return (ret);
}

static int
compare_props(const void *a, const void *b, zfs_prop_t prop)
{
        const prop_changenode_t *ca = a;
        const prop_changenode_t *cb = b;

        char propa[MAXPATHLEN];
        char propb[MAXPATHLEN];

        boolean_t haspropa, haspropb;

        haspropa = (zfs_prop_get(ca->cn_handle, prop, propa, sizeof (propa),
            NULL, NULL, 0, B_FALSE) == 0);
        haspropb = (zfs_prop_get(cb->cn_handle, prop, propb, sizeof (propb),
            NULL, NULL, 0, B_FALSE) == 0);

        if (!haspropa && haspropb)
                return (-1);
        else if (haspropa && !haspropb)
                return (1);
        else if (!haspropa && !haspropb)
                return (0);
        else
                return (strcmp(propb, propa));
}

static int
compare_mountpoints(const void *a, const void *b, void *unused)
{
        /*
         * When unsharing or unmounting filesystems, we need to do it in
         * mountpoint order.  This allows the user to have a mountpoint
         * hierarchy that is different from the dataset hierarchy, and still
         * allow it to be changed.
         */
        (void) unused;
        return (compare_props(a, b, ZFS_PROP_MOUNTPOINT));
}

static int
compare_dataset_names(const void *a, const void *b, void *unused)
{
        (void) unused;
        return (compare_props(a, b, ZFS_PROP_NAME));
}

/*
 * Given a ZFS handle and a property, construct a complete list of datasets
 * that need to be modified as part of this process.  For anything but the
 * 'mountpoint' and 'sharenfs' properties, this just returns an empty list.
 * Otherwise, we iterate over all children and look for any datasets that
 * inherit the property.  For each such dataset, we add it to the list and
 * mark whether it was shared beforehand.
 */
prop_changelist_t *
changelist_gather(zfs_handle_t *zhp, zfs_prop_t prop, int gather_flags,
    int mnt_flags)
{
        prop_changelist_t *clp;
        prop_changenode_t *cn;
        zfs_handle_t *temp;
        char property[ZFS_MAXPROPLEN];
        boolean_t legacy = B_FALSE;

        clp = zfs_alloc(zhp->zfs_hdl, sizeof (prop_changelist_t));

        /*
         * For mountpoint-related tasks, we want to sort everything by
         * mountpoint, so that we mount and unmount them in the appropriate
         * order, regardless of their position in the hierarchy.
         */
        if (prop == ZFS_PROP_NAME || prop == ZFS_PROP_ZONED ||
            prop == ZFS_PROP_MOUNTPOINT || prop == ZFS_PROP_SHARENFS ||
            prop == ZFS_PROP_SHARESMB) {

                if (zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT,
                    property, sizeof (property),
                    NULL, NULL, 0, B_FALSE) == 0 &&
                    (strcmp(property, "legacy") == 0 ||
                    strcmp(property, "none") == 0)) {
                        legacy = B_TRUE;
                }
        }

        clp->cl_pool = uu_avl_pool_create("changelist_pool",
            sizeof (prop_changenode_t),
            offsetof(prop_changenode_t, cn_treenode),
            legacy ? compare_dataset_names : compare_mountpoints, 0);
        if (clp->cl_pool == NULL) {
                assert(uu_error() == UU_ERROR_NO_MEMORY);
                (void) zfs_error(zhp->zfs_hdl, EZFS_NOMEM, "internal error");
                changelist_free(clp);
                return (NULL);
        }

        clp->cl_tree = uu_avl_create(clp->cl_pool, NULL, UU_DEFAULT);
        clp->cl_gflags = gather_flags;
        clp->cl_mflags = mnt_flags;

        if (clp->cl_tree == NULL) {
                assert(uu_error() == UU_ERROR_NO_MEMORY);
                (void) zfs_error(zhp->zfs_hdl, EZFS_NOMEM, "internal error");
                changelist_free(clp);
                return (NULL);
        }

        /*
         * If this is a rename or the 'zoned' property, we pretend we're
         * changing the mountpoint and flag it so we can catch all children in
         * change_one().
         *
         * Flag cl_alldependents to catch all children plus the dependents
         * (clones) that are not in the hierarchy.
         */
        if (prop == ZFS_PROP_NAME) {
                clp->cl_prop = ZFS_PROP_MOUNTPOINT;
                clp->cl_alldependents = B_TRUE;
        } else if (prop == ZFS_PROP_ZONED) {
                clp->cl_prop = ZFS_PROP_MOUNTPOINT;
                clp->cl_allchildren = B_TRUE;
        } else if (prop == ZFS_PROP_CANMOUNT) {
                clp->cl_prop = ZFS_PROP_MOUNTPOINT;
        } else if (prop == ZFS_PROP_VOLSIZE) {
                clp->cl_prop = ZFS_PROP_MOUNTPOINT;
        } else {
                clp->cl_prop = prop;
        }
        clp->cl_realprop = prop;

        if (clp->cl_prop != ZFS_PROP_MOUNTPOINT &&
            clp->cl_prop != ZFS_PROP_SHARENFS &&
            clp->cl_prop != ZFS_PROP_SHARESMB)
                return (clp);

        /*
         * If watching SHARENFS or SHARESMB then
         * also watch its companion property.
         */
        if (clp->cl_prop == ZFS_PROP_SHARENFS)
                clp->cl_shareprop = ZFS_PROP_SHARESMB;
        else if (clp->cl_prop == ZFS_PROP_SHARESMB)
                clp->cl_shareprop = ZFS_PROP_SHARENFS;

        if (clp->cl_prop == ZFS_PROP_MOUNTPOINT &&
            (clp->cl_gflags & CL_GATHER_ITER_MOUNTED)) {
                /*
                 * Instead of iterating through all of the dataset children we
                 * gather mounted dataset children from MNTTAB
                 */
                if (zfs_iter_mounted(zhp, changelist_add_mounted, clp) != 0) {
                        changelist_free(clp);
                        return (NULL);
                }
        } else if (clp->cl_alldependents) {
                if (zfs_iter_dependents_v2(zhp, 0, B_TRUE, change_one,
                    clp) != 0) {
                        changelist_free(clp);
                        return (NULL);
                }
        } else if (zfs_iter_children_v2(zhp, 0, change_one, clp) != 0) {
                changelist_free(clp);
                return (NULL);
        }

        /*
         * We have to re-open ourselves because we auto-close all the handles
         * and can't tell the difference.
         */
        if ((temp = zfs_open(zhp->zfs_hdl, zfs_get_name(zhp),
            ZFS_TYPE_DATASET)) == NULL) {
                changelist_free(clp);
                return (NULL);
        }

        /*
         * Always add ourself to the list.  We add ourselves to the end so that
         * we're the last to be unmounted.
         */
        cn = zfs_alloc(zhp->zfs_hdl, sizeof (prop_changenode_t));
        cn->cn_handle = temp;
        cn->cn_mounted = (clp->cl_gflags & CL_GATHER_MOUNT_ALWAYS) ||
            zfs_is_mounted(temp, NULL);
        cn->cn_shared = zfs_is_shared(temp, NULL, NULL);
        cn->cn_zoned = zfs_prop_get_int(zhp, ZFS_PROP_ZONED);
        cn->cn_needpost = B_TRUE;

        uu_avl_node_init(cn, &cn->cn_treenode, clp->cl_pool);
        uu_avl_index_t idx;
        if (uu_avl_find(clp->cl_tree, cn, NULL, &idx) == NULL) {
                uu_avl_insert(clp->cl_tree, cn, idx);
        } else {
                free(cn);
                zfs_close(temp);
        }

        /*
         * If the mountpoint property was previously 'legacy', or 'none',
         * record it as the behavior of changelist_postfix() will be different.
         */
        if ((clp->cl_prop == ZFS_PROP_MOUNTPOINT) && legacy) {
                /*
                 * do not automatically mount ex-legacy datasets if
                 * we specifically set canmount to noauto
                 */
                if (zfs_prop_get_int(zhp, ZFS_PROP_CANMOUNT) !=
                    ZFS_CANMOUNT_NOAUTO)
                        clp->cl_waslegacy = B_TRUE;
        }

        return (clp);
}