diff --git a/repair/phase5.c b/repair/phase5.c
index 15358597..4470f63a 100644
--- a/repair/phase5.c
+++ b/repair/phase5.c
@@ -20,6 +20,11 @@
 #include "rmap.h"
 #include "bload.h"
 
+struct lost_fsb {
+	xfs_fsblock_t		fsbno;
+	xfs_extlen_t		len;
+};
+
 struct bt_rebuild {
 	struct xrep_newbt	newbt;
 	struct xfs_btree_bload	bload;
@@ -301,21 +306,24 @@ static void
 finish_rebuild(
 	struct xfs_mount	*mp,
 	struct bt_rebuild	*btr,
-	struct xfs_slab		*lost_fsb)
+	struct xfs_slab		*lost_fsbs)
 {
 	struct xrep_newbt_resv	*resv, *n;
 
 	for_each_xrep_newbt_reservation(&btr->newbt, resv, n) {
-		while (resv->used < resv->len) {
-			xfs_fsblock_t	fsb = resv->fsbno + resv->used;
-			int		error;
+		struct lost_fsb	lost;
+		int		error;
 
-			error = slab_add(lost_fsb, &fsb);
-			if (error)
-				do_error(
+		if (resv->used == resv->len)
+			continue;
+
+		lost.fsbno = resv->fsbno + resv->used;
+		lost.len = resv->len - resv->used;
+		error = slab_add(lost_fsbs, &lost);
+		if (error)
+			do_error(
 _("Insufficient memory saving lost blocks.\n"));
-			resv->used++;
-		}
+		resv->used = resv->len;
 	}
 
 	xrep_newbt_destroy(&btr->newbt, 0);
@@ -1044,7 +1052,7 @@ build_agf_agfl(
 	int			lostblocks,	/* # blocks that will be lost */
 	struct bt_rebuild	*btr_rmap,
 	struct bt_rebuild	*btr_refcount,
-	struct xfs_slab		*lost_fsb)
+	struct xfs_slab		*lost_fsbs)
 {
 	struct extent_tree_node	*ext_ptr;
 	struct xfs_buf		*agf_buf, *agfl_buf;
@@ -1253,7 +1261,7 @@ static void
 phase5_func(
 	struct xfs_mount	*mp,
 	xfs_agnumber_t		agno,
-	struct xfs_slab		*lost_fsb)
+	struct xfs_slab		*lost_fsbs)
 {
 	struct repair_ctx	sc = { .mp = mp, };
 	struct agi_stat		agi_stat = {0,};
@@ -1388,7 +1396,7 @@ phase5_func(
 	 * set up agf and agfl
 	 */
 	build_agf_agfl(mp, agno, &btr_bno, &btr_cnt, freeblks1, extra_blocks,
-			&btr_rmap, &btr_refcount, lost_fsb);
+			&btr_rmap, &btr_refcount, lost_fsbs);
 
 	/*
 	 * build inode allocation trees.
@@ -1403,15 +1411,15 @@ phase5_func(
 	/*
 	 * tear down cursors
 	 */
-	finish_rebuild(mp, &btr_bno, lost_fsb);
-	finish_rebuild(mp, &btr_cnt, lost_fsb);
-	finish_rebuild(mp, &btr_ino, lost_fsb);
+	finish_rebuild(mp, &btr_bno, lost_fsbs);
+	finish_rebuild(mp, &btr_cnt, lost_fsbs);
+	finish_rebuild(mp, &btr_ino, lost_fsbs);
 	if (xfs_sb_version_hasfinobt(&mp->m_sb))
-		finish_rebuild(mp, &btr_fino, lost_fsb);
+		finish_rebuild(mp, &btr_fino, lost_fsbs);
 	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
-		finish_rebuild(mp, &btr_rmap, lost_fsb);
+		finish_rebuild(mp, &btr_rmap, lost_fsbs);
 	if (xfs_sb_version_hasreflink(&mp->m_sb))
-		finish_rebuild(mp, &btr_refcount, lost_fsb);
+		finish_rebuild(mp, &btr_refcount, lost_fsbs);
 
 	/*
 	 * release the incore per-AG bno/bcnt trees so
@@ -1431,19 +1439,19 @@ inject_lost_blocks(
 {
 	struct xfs_trans	*tp = NULL;
 	struct xfs_slab_cursor	*cur = NULL;
-	xfs_fsblock_t		*fsb;
+	struct lost_fsb		*lost;
 	int			error;
 
 	error = init_slab_cursor(lost_fsbs, NULL, &cur);
 	if (error)
 		return error;
 
-	while ((fsb = pop_slab_cursor(cur)) != NULL) {
+	while ((lost = pop_slab_cursor(cur)) != NULL) {
 		error = -libxfs_trans_alloc_rollable(mp, 16, &tp);
 		if (error)
 			goto out_cancel;
 
-		error = -libxfs_free_extent(tp, *fsb, 1,
+		error = -libxfs_free_extent(tp, lost->fsbno, lost->len,
 				&XFS_RMAP_OINFO_ANY_OWNER, XFS_AG_RESV_NONE);
 		if (error)
 			goto out_cancel;
@@ -1464,7 +1472,7 @@ inject_lost_blocks(
 void
 phase5(xfs_mount_t *mp)
 {
-	struct xfs_slab		*lost_fsb;
+	struct xfs_slab		*lost_fsbs;
 	xfs_agnumber_t		agno;
 	int			error;
 
@@ -1507,12 +1515,12 @@ phase5(xfs_mount_t *mp)
 	if (sb_fdblocks_ag == NULL)
 		do_error(_("cannot alloc sb_fdblocks_ag buffers\n"));
 
-	error = init_slab(&lost_fsb, sizeof(xfs_fsblock_t));
+	error = init_slab(&lost_fsbs, sizeof(struct lost_fsb));
 	if (error)
 		do_error(_("cannot alloc lost block slab\n"));
 
 	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++)
-		phase5_func(mp, agno, lost_fsb);
+		phase5_func(mp, agno, lost_fsbs);
 
 	print_final_rpt();
 
@@ -1555,10 +1563,10 @@ _("unable to add AG %u reverse-mapping data to btree.\n"), agno);
 	 * Put blocks that were unnecessarily reserved for btree
 	 * reconstruction back into the filesystem free space data.
 	 */
-	error = inject_lost_blocks(mp, lost_fsb);
+	error = inject_lost_blocks(mp, lost_fsbs);
 	if (error)
 		do_error(_("Unable to reinsert lost blocks into filesystem.\n"));
-	free_slab(&lost_fsb);
+	free_slab(&lost_fsbs);
 
 	bad_ino_btree = 0;
 
