Index: head/lib/libgeom/geom_getxml.c
===================================================================
--- head/lib/libgeom/geom_getxml.c	(revision 271084)
+++ head/lib/libgeom/geom_getxml.c	(revision 271085)
@@ -1,60 +1,87 @@
 /*-
  * Copyright (c) 2003 Poul-Henning Kamp
  * All rights reserved.
  *
  * 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. The names of the authors may not 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.
  *
  * $FreeBSD$
  */
 
 #include <sys/types.h>
 #include <sys/sysctl.h>
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 #include "libgeom.h"
 
+/*
+ * Amount of extra space we allocate to try and anticipate the size of
+ * confxml.
+ */
+#define	GEOM_GETXML_SLACK	4096
+
+/*
+ * Number of times to retry in the face of the size of confxml exceeding
+ * that of our buffer.
+ */
+#define	GEOM_GETXML_RETRIES	4
+
 char *
 geom_getxml(void)
 {
 	char *p;
 	size_t l = 0;
 	int mib[3];
 	size_t sizep;
+	int retries;
 
 	sizep = sizeof(mib) / sizeof(*mib);
 	if (sysctlnametomib("kern.geom.confxml", mib, &sizep) != 0)
 		return (NULL);
 	if (sysctl(mib, sizep, NULL, &l, NULL, 0) != 0)
 		return (NULL);
-	l += 4096;
-	p = malloc(l);
-	if (p == NULL)
-		return (NULL);
-	if (sysctl(mib, sizep, p, &l, NULL, 0) != 0) {
+	l += GEOM_GETXML_SLACK;
+
+	for (retries = 0; retries < GEOM_GETXML_RETRIES; retries++) {
+		p = malloc(l);
+		if (p == NULL)
+			return (NULL);
+		if (sysctl(mib, sizep, p, &l, NULL, 0) == 0)
+			return (reallocf(p, strlen(p) + 1));
+
 		free(p);
-		return (NULL);
+
+		if (errno != ENOMEM)
+			return (NULL);
+
+		/*
+		 * Our buffer wasn't big enough. Make it bigger and
+		 * try again.
+		 */
+		l *= 2;
 	}
-	return (reallocf(p, strlen(p) + 1));
+
+	return (NULL);
 }