commit 1ff2951300260c66cadf1b8d58222f1c60c522a2
Author: cem <cem@FreeBSD.org>
Date:   Sun Sep 24 19:59:26 2017 +0000

    g_resize_provider_event: Do not invoke orphan method twice
    
    Like r266444, g_resize_provider_event can attempt to orphan an already
    orphaned geom_dev consumer.  This will cause a panic in g_dev_orphan.  Apply
    the same fix as was applied to g_orphan_register.
    
    Reviewed by:    ae
    Sponsored by:   Dell EMC Isilon
    Differential Revision:  https://reviews.freebsd.org/D12469

Notes:
    svn path=/head/; revision=323977

diff --git a/sys/geom/geom_subr.c b/sys/geom/geom_subr.c
index e1fd0296c31f..10d82d0b8c6b 100644
--- a/sys/geom/geom_subr.c
+++ b/sys/geom/geom_subr.c
@@ -631,6 +631,14 @@ g_resize_provider_event(void *arg, int flag)
 	LIST_FOREACH_SAFE(cp, &pp->consumers, consumers, cp2) {
 		gp = cp->geom;
 		if (gp->resize == NULL && size < pp->mediasize) {
+			/*
+			 * XXX: g_dev_orphan method does deferred destroying
+			 * and it is possible, that other event could already
+			 * call the orphan method. Check consumer's flags to
+			 * do not schedule it twice.
+			 */
+			if (cp->flags & G_CF_ORPHAN)
+				continue;
 			cp->flags |= G_CF_ORPHAN;
 			cp->geom->orphan(cp);
 		}