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	Index: head/lib/libbe/be.h
	===================================================================
	--- head/lib/libbe/be.h
	+++ head/lib/libbe/be.h
	@@ -60,6 +60,7 @@
	BE_ERR_NOMEM, /* insufficient memory */
	BE_ERR_UNKNOWN, /* unknown error */
	BE_ERR_INVORIGIN, /* invalid origin */
	+ BE_ERR_HASCLONES, /* snapshot has clones */
	} be_error_t;


	Index: head/lib/libbe/be.c
	===================================================================
	--- head/lib/libbe/be.c
	+++ head/lib/libbe/be.c
	@@ -33,7 +33,7 @@
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <sys/ucred.h>
	-
	+#include <sys/queue.h>
	#include <sys/zfs_context.h>
	#include <sys/mntent.h>

	@@ -48,9 +48,16 @@
	#include "be.h"
	#include "be_impl.h"

	+struct promote_entry {
	+ char name[BE_MAXPATHLEN];
	+ SLIST_ENTRY(promote_entry) link;
	+};
	+
	struct be_destroy_data {
	- libbe_handle_t *lbh;
	- char *snapname;
	+ libbe_handle_t *lbh;
	+ char target_name[BE_MAXPATHLEN];
	+ char *snapname;
	+ SLIST_HEAD(, promote_entry) promotelist;
	};

	#if SOON
	@@ -194,7 +201,153 @@
	zfs_nicenum(num, buf, buflen);
	}

	+static bool
	+be_should_promote_clones(zfs_handle_t zfs_hdl, struct be_destroy_data bdd)
	+{
	+ char *atpos;
	+
	+ if (zfs_get_type(zfs_hdl) != ZFS_TYPE_SNAPSHOT)
	+ return (false);
	+
	+ /*
	+ * If we're deleting a snapshot, we need to make sure we only promote
	+ * clones that are derived from one of the snapshots we're deleting,
	+ * rather than that of a snapshot we're not touching. This keeps stuff
	+ * in a consistent state, making sure that we don't error out unless
	+ * we really need to.
	+ */
	+ if (bdd->snapname == NULL)
	+ return (true);
	+
	+ atpos = strchr(zfs_get_name(zfs_hdl), '@');
	+ return (strcmp(atpos + 1, bdd->snapname) == 0);
	+}
	+
	+/*
	+ * This is executed from be_promote_dependent_clones via zfs_iter_dependents,
	+ * It checks if the dependent type is a snapshot then attempts to find any
	+ * clones associated with it. Any clones not related to the destroy target are
	+ * added to the promote list.
	+ */
	static int
	+be_dependent_clone_cb(zfs_handle_t zfs_hdl, void data)
	+{
	+ int err;
	+ bool found;
	+ char *name;
	+ struct nvlist *nvl;
	+ struct nvpair *nvp;
	+ struct be_destroy_data *bdd;
	+ struct promote_entry entry, newentry;
	+
	+ nvp = NULL;
	+ err = 0;
	+ bdd = (struct be_destroy_data *)data;
	+
	+ if (be_should_promote_clones(zfs_hdl, bdd) &&
	+ (nvl = zfs_get_clones_nvl(zfs_hdl)) != NULL) {
	+ while ((nvp = nvlist_next_nvpair(nvl, nvp)) != NULL) {
	+ name = nvpair_name(nvp);
	+
	+ /*
	+ * Skip if the clone is equal to, or a child of, the
	+ * destroy target.
	+ */
	+ if (strncmp(name, bdd->target_name,
	+ strlen(bdd->target_name)) == 0 \|\|
	+ strstr(name, bdd->target_name) == name) {
	+ continue;
	+ }
	+
	+ found = false;
	+ SLIST_FOREACH(entry, &bdd->promotelist, link) {
	+ if (strcmp(entry->name, name) == 0) {
	+ found = true;
	+ break;
	+ }
	+ }
	+
	+ if (found)
	+ continue;
	+
	+ newentry = malloc(sizeof(struct promote_entry));
	+ if (newentry == NULL) {
	+ err = ENOMEM;
	+ break;
	+ }
	+
	+#define BE_COPY_NAME(entry, src) \
	+ strlcpy((entry)->name, (src), sizeof((entry)->name))
	+ if (BE_COPY_NAME(newentry, name) >=
	+ sizeof(newentry->name)) {
	+ /* Shouldn't happen. */
	+ free(newentry);
	+ err = ENAMETOOLONG;
	+ break;
	+ }
	+#undef BE_COPY_NAME
	+
	+ /*
	+ * We're building up a SLIST here to make sure both that
	+ * we get the order right and so that we don't
	+ * inadvertently observe the wrong state by promoting
	+ * datasets while we're still walking the tree. The
	+ * latter can lead to situations where we promote a BE
	+ * then effectively demote it again.
	+ */
	+ SLIST_INSERT_HEAD(&bdd->promotelist, newentry, link);
	+ }
	+ nvlist_free(nvl);
	+ }
	+ zfs_close(zfs_hdl);
	+ return (err);
	+}
	+
	+/*
	+ * This is called before a destroy, so that any datasets(environments) that are
	+ * dependent on this one get promoted before destroying the target.
	+ */
	+static int
	+be_promote_dependent_clones(zfs_handle_t zfs_hdl, struct be_destroy_data bdd)
	+{
	+ int err;
	+ zfs_handle_t *clone;
	+ struct promote_entry *entry;
	+
	+ snprintf(bdd->target_name, BE_MAXPATHLEN, "%s/", zfs_get_name(zfs_hdl));
	+ err = zfs_iter_dependents(zfs_hdl, true, be_dependent_clone_cb, bdd);
	+
	+ /*
	+ * Drain the list and walk away from it if we're only deleting a
	+ * snapshot.
	+ */
	+ if (bdd->snapname != NULL && !SLIST_EMPTY(&bdd->promotelist))
	+ err = BE_ERR_HASCLONES;
	+ while (!SLIST_EMPTY(&bdd->promotelist)) {
	+ entry = SLIST_FIRST(&bdd->promotelist);
	+ SLIST_REMOVE_HEAD(&bdd->promotelist, link);
	+
	+#define ZFS_GRAB_CLONE() \
	+ zfs_open(bdd->lbh->lzh, entry->name, ZFS_TYPE_FILESYSTEM)
	+ /*
	+ * Just skip this part on error, we still want to clean up the
	+ * promotion list after the first error. We'll then preserve it
	+ * all the way back.
	+ */
	+ if (err == 0 && (clone = ZFS_GRAB_CLONE()) != NULL) {
	+ err = zfs_promote(clone);
	+ if (err != 0)
	+ err = BE_ERR_DESTROYMNT;
	+ zfs_close(clone);
	+ }
	+#undef ZFS_GRAB_CLONE
	+ free(entry);
	+ }
	+
	+ return (err);
	+}
	+
	+static int
	be_destroy_cb(zfs_handle_t zfs_hdl, void data)
	{
	char path[BE_MAXPATHLEN];
	@@ -239,8 +392,9 @@
	* BE_DESTROY_FORCE : forces operation on mounted datasets
	* BE_DESTROY_ORIGIN: destroy the origin snapshot as well
	*/
	-int
	-be_destroy(libbe_handle_t lbh, const char name, int options)
	+static int
	+be_destroy_internal(libbe_handle_t lbh, const char name, int options,
	+ bool odestroyer)
	{
	struct be_destroy_data bdd;
	char origin[BE_MAXPATHLEN], path[BE_MAXPATHLEN];
	@@ -251,6 +405,7 @@

	bdd.lbh = lbh;
	bdd.snapname = NULL;
	+ SLIST_INIT(&bdd.promotelist);
	force = options & BE_DESTROY_FORCE;
	*origin = '\0';

	@@ -268,25 +423,6 @@
	if (fs == NULL)
	return (set_error(lbh, BE_ERR_ZFSOPEN));

	- if ((options & BE_DESTROY_WANTORIGIN) != 0 &&
	- zfs_prop_get(fs, ZFS_PROP_ORIGIN, origin, sizeof(origin),
	- NULL, NULL, 0, 1) != 0 &&
	- (options & BE_DESTROY_ORIGIN) != 0)
	- return (set_error(lbh, BE_ERR_NOORIGIN));
	-
	- /*
	- * If the caller wants auto-origin destruction and the origin
	- * name matches one of our automatically created snapshot names
	- * (i.e. strftime("%F-%T") with a serial at the end), then
	- * we'll set the DESTROY_ORIGIN flag and nuke it
	- * be_is_auto_snapshot_name is exported from libbe(3) so that
	- * the caller can determine if it needs to warn about the origin
	- * not being destroyed or not.
	- */
	- if ((options & BE_DESTROY_AUTOORIGIN) != 0 && *origin != '\0' &&
	- be_is_auto_snapshot_name(lbh, origin))
	- options \|= BE_DESTROY_ORIGIN;
	-
	/* Don't destroy a mounted dataset unless force is specified */
	if ((mounted = zfs_is_mounted(fs, NULL)) != 0) {
	if (force) {
	@@ -297,6 +433,14 @@
	}
	}
	} else {
	+ /*
	+ * If we're initially destroying a snapshot, origin options do
	+ * not make sense. If we're destroying the origin snapshot of
	+ * a BE, we want to maintain the options in case we need to
	+ * fake success after failing to promote.
	+ */
	+ if (!odestroyer)
	+ options &= ~BE_DESTROY_WANTORIGIN;
	if (!zfs_dataset_exists(lbh->lzh, path, ZFS_TYPE_SNAPSHOT))
	return (set_error(lbh, BE_ERR_NOENT));

	@@ -311,6 +455,49 @@
	}
	}

	+ /*
	+ * Whether we're destroying a BE or a single snapshot, we need to walk
	+ * the tree of what we're going to destroy and promote everything in our
	+ * path so that we can make it happen.
	+ */
	+ if ((err = be_promote_dependent_clones(fs, &bdd)) != 0) {
	+ free(bdd.snapname);
	+
	+ /*
	+ * If we're just destroying the origin of some other dataset
	+ * we were invoked to destroy, then we just ignore
	+ * BE_ERR_HASCLONES and return success unless the caller wanted
	+ * to force the issue.
	+ */
	+ if (odestroyer && err == BE_ERR_HASCLONES &&
	+ (options & BE_DESTROY_AUTOORIGIN) != 0)
	+ return (0);
	+ return (set_error(lbh, err));
	+ }
	+
	+ /*
	+ * This was deferred until after we promote all of the derivatives so
	+ * that we grab the new origin after everything's settled down.
	+ */
	+ if ((options & BE_DESTROY_WANTORIGIN) != 0 &&
	+ zfs_prop_get(fs, ZFS_PROP_ORIGIN, origin, sizeof(origin),
	+ NULL, NULL, 0, 1) != 0 &&
	+ (options & BE_DESTROY_ORIGIN) != 0)
	+ return (set_error(lbh, BE_ERR_NOORIGIN));
	+
	+ /*
	+ * If the caller wants auto-origin destruction and the origin
	+ * name matches one of our automatically created snapshot names
	+ * (i.e. strftime("%F-%T") with a serial at the end), then
	+ * we'll set the DESTROY_ORIGIN flag and nuke it
	+ * be_is_auto_snapshot_name is exported from libbe(3) so that
	+ * the caller can determine if it needs to warn about the origin
	+ * not being destroyed or not.
	+ */
	+ if ((options & BE_DESTROY_AUTOORIGIN) != 0 && *origin != '\0' &&
	+ be_is_auto_snapshot_name(lbh, origin))
	+ options \|= BE_DESTROY_ORIGIN;
	+
	err = be_destroy_cb(fs, &bdd);
	zfs_close(fs);
	free(bdd.snapname);
	@@ -337,8 +524,23 @@
	if (strncmp(origin, lbh->root, rootlen) != 0 \|\| origin[rootlen] != '/')
	return (0);

	- return (be_destroy(lbh, origin + rootlen + 1,
	- options & ~BE_DESTROY_ORIGIN));
	+ return (be_destroy_internal(lbh, origin + rootlen + 1,
	+ options & ~BE_DESTROY_ORIGIN, true));
	+}
	+
	+int
	+be_destroy(libbe_handle_t lbh, const char name, int options)
	+{
	+
	+ /*
	+ * The consumer must not set both BE_DESTROY_AUTOORIGIN and
	+ * BE_DESTROY_ORIGIN. Internally, we'll set the latter from the former.
	+ * The latter should imply that we must succeed at destroying the
	+ * origin, or complain otherwise.
	+ */
	+ if ((options & BE_DESTROY_WANTORIGIN) == BE_DESTROY_WANTORIGIN)
	+ return (set_error(lbh, BE_ERR_UNKNOWN));
	+ return (be_destroy_internal(lbh, name, options, false));
	}

	static void
	Index: head/lib/libbe/be_error.c
	===================================================================
	--- head/lib/libbe/be_error.c
	+++ head/lib/libbe/be_error.c
	@@ -108,6 +108,9 @@
	case BE_ERR_INVORIGIN:
	return ("invalid origin");

	+ case BE_ERR_HASCLONES:
	+ return ("snapshot has clones");
	+
	default:
	assert(lbh->error == BE_ERR_SUCCESS);
	return ("no error");
	Index: head/sbin/bectl/tests/bectl_test.sh
	===================================================================
	--- head/sbin/bectl/tests/bectl_test.sh
	+++ head/sbin/bectl/tests/bectl_test.sh
	@@ -162,6 +162,51 @@
	atf_check bectl -r ${zpool}/ROOT create -e default default3
	atf_check bectl -r ${zpool}/ROOT destroy -o default3
	atf_check bectl -r ${zpool}/ROOT unmount default
	+
	+ # create two be from the same parent and destroy the parent
	+ atf_check bectl -r ${zpool}/ROOT create -e default default2
	+ atf_check bectl -r ${zpool}/ROOT create -e default default3
	+ atf_check bectl -r ${zpool}/ROOT destroy default
	+ atf_check bectl -r ${zpool}/ROOT destroy default2
	+ atf_check bectl -r ${zpool}/ROOT rename default3 default
	+
	+ # Create a BE, have it be the parent for another and repeat, then start
	+ # deleting environments. Arbitrarily chose default3 as the first.
	+ # Sleeps are required to prevent conflicting snapshots- libbe will
	+ # use the time with a serial at the end as needed to prevent collisions,
	+ # but as BEs get promoted the snapshot names will convert and conflict
	+ # anyways. libbe should perhaps consider adding something extra to the
	+ # default name to prevent collisions like this, but the default name
	+ # includes down to the second and creating BEs this rapidly is perhaps
	+ # uncommon enough.
	+ atf_check bectl -r ${zpool}/ROOT create -e default default2
	+ sleep 1
	+ atf_check bectl -r ${zpool}/ROOT create -e default2 default3
	+ sleep 1
	+ atf_check bectl -r ${zpool}/ROOT create -e default3 default4
	+ atf_check bectl -r ${zpool}/ROOT destroy default3
	+ atf_check bectl -r ${zpool}/ROOT destroy default2
	+ atf_check bectl -r ${zpool}/ROOT destroy default4
	+
	+ # Create two BEs, then create an unrelated snapshot on the originating
	+ # BE and destroy it. We shouldn't have promoted the second BE, and it's
	+ # only possible to tell if we promoted it by making sure we didn't
	+ # demote the first BE at some point -- if we did, it's origin will no
	+ # longer be empty.
	+ atf_check bectl -r ${zpool}/ROOT create -e default default2
	+ atf_check bectl -r ${zpool}/ROOT create default@test
	+
	+ atf_check bectl -r ${zpool}/ROOT destroy default@test
	+ atf_check -o inline:"-\n" zfs get -Ho value origin ${zpool}/ROOT/default
	+ atf_check bectl -r ${zpool}/ROOT destroy default2
	+
	+ # As observed by beadm, if we explicitly try to destroy a snapshot that
	+ # leads to clones, we shouldn't have allowed it.
	+ atf_check bectl -r ${zpool}/ROOT create default@test
	+ atf_check bectl -r ${zpool}/ROOT create -e default@test default2
	+
	+ atf_check -e not-empty -s not-exit:0 bectl -r ${zpool}/ROOT destroy \
	+ default@test
	}
	bectl_destroy_cleanup()
	{

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