Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -103,6 +103,7 @@
 #include <sys/malloc.h>
 #include <stdio.h>
 #include <string.h>
+#include <stddef.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <stdbool.h>
@@ -133,7 +134,7 @@
 static daddr_t blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count);
 static daddr_t blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count,
 		    daddr_t radix, daddr_t blk);
-static daddr_t	blst_radix_init(blmeta_t *scan, daddr_t radix, daddr_t count);
+static void	blst_radix_init(blmeta_t *scan, daddr_t radix, daddr_t count);
 #ifndef _KERNEL
 static void	blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix,
 		    int tab);
@@ -142,6 +143,7 @@
 #ifdef _KERNEL
 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
 #endif
+#define	BLIST_META_MASK (BLIST_META_RADIX - 1)
 
 CTASSERT(BLIST_BMAP_RADIX % BLIST_META_RADIX == 0);
 
@@ -183,29 +185,41 @@
 blist_create(daddr_t blocks, int flags)
 {
 	blist_t bl;
-	daddr_t nodes, radix;
+	daddr_t i, last_block, nodes, radix;
 
 	/*
-	 * Calculate the radix field used for scanning.
+	 * Calculate the radix and node count used for scanning.  Find the last
+	 * block that is followed by a terminator.
 	 */
+	last_block = blocks - 1;
 	radix = BLIST_BMAP_RADIX;
 	while (radix < blocks) {
+		if (((last_block / radix + 1) & BLIST_META_MASK) != 0)
+			/*
+			 * A terminator will be added.  Update last_block to the
+			 * position just before that terminator.
+			 */
+			last_block |= radix - 1;
 		radix *= BLIST_META_RADIX;
 	}
-	nodes = 1 + blst_radix_init(NULL, radix, blocks);
 
-	bl = malloc(sizeof(struct blist), M_SWAP, flags);
+	/*
+	 * Count the meta-nodes in the expanded tree, including the final
+	 * terminator, from the bottom level up to the root.
+	 */
+	nodes = (last_block >= blocks) ? 2: 1;
+	last_block /= BLIST_BMAP_RADIX;
+	while (last_block > 0) {
+		nodes += last_block + 1;
+		last_block /= BLIST_META_RADIX;
+	}
+	bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags);
 	if (bl == NULL)
 		return (NULL);
 
 	bl->bl_blocks = blocks;
 	bl->bl_radix = radix;
 	bl->bl_cursor = 0;
-	bl->bl_root = malloc(nodes * sizeof(blmeta_t), M_SWAP, flags);
-	if (bl->bl_root == NULL) {
-		free(bl, M_SWAP);
-		return (NULL);
-	}
 	blst_radix_init(bl->bl_root, radix, blocks);
 
 #if defined(BLIST_DEBUG)
@@ -226,7 +240,6 @@
 void
 blist_destroy(blist_t bl)
 {
-	free(bl->bl_root, M_SWAP);
 	free(bl, M_SWAP);
 }
 
@@ -832,23 +845,19 @@
  *	be considerably less than the calculated radix due to the large
  *	RADIX values we use.
  */
-static daddr_t
+static void
 blst_radix_init(blmeta_t *scan, daddr_t radix, daddr_t count)
 {
-	daddr_t i, memindex, next_skip, skip;
-
-	memindex = 0;
+	daddr_t i, next_skip, skip;
 
 	/*
 	 * Leaf node
 	 */
 
 	if (radix == BLIST_BMAP_RADIX) {
-		if (scan) {
-			scan->bm_bighint = 0;
-			scan->u.bmu_bitmap = 0;
-		}
-		return (memindex);
+		scan->bm_bighint = 0;
+		scan->u.bmu_bitmap = 0;
+		return;
 	}
 
 	/*
@@ -857,10 +866,8 @@
 	 * is required to manage 'count' blocks, so we continue on anyway.
 	 */
 
-	if (scan) {
-		scan->bm_bighint = 0;
-		scan->u.bmu_avail = 0;
-	}
+	scan->bm_bighint = 0;
+	scan->u.bmu_avail = 0;
 
 	skip = radix_to_skip(radix);
 	next_skip = skip / BLIST_META_RADIX;
@@ -871,30 +878,22 @@
 			/*
 			 * Allocate the entire object
 			 */
-			memindex = i +
-			    blst_radix_init(((scan) ? &scan[i] : NULL), radix,
-			    radix);
+			blst_radix_init(&scan[i], radix, radix);
 			count -= radix;
 		} else if (count > 0) {
 			/*
 			 * Allocate a partial object
 			 */
-			memindex = i +
-			    blst_radix_init(((scan) ? &scan[i] : NULL), radix,
-			    count);
+			blst_radix_init(&scan[i], radix, count);
 			count = 0;
 		} else {
 			/*
 			 * Add terminator and break out
 			 */
-			if (scan)
-				scan[i].bm_bighint = (daddr_t)-1;
+			scan[i].bm_bighint = (daddr_t)-1;
 			break;
 		}
 	}
-	if (memindex < i)
-		memindex = i;
-	return (memindex);
 }
 
 #ifdef BLIST_DEBUG
Index: sys/sys/blist.h
===================================================================
--- sys/sys/blist.h
+++ sys/sys/blist.h
@@ -82,7 +82,7 @@
 	daddr_t		bl_blocks;	/* area of coverage		*/
 	daddr_t		bl_radix;	/* coverage radix		*/
 	daddr_t		bl_cursor;	/* next-fit search starts at	*/
-	blmeta_t	*bl_root;	/* root of radix tree		*/
+	blmeta_t	bl_root[1];	/* root of radix tree		*/
 } *blist_t;
 
 #define BLIST_META_RADIX	16