diff --git a/kmod/src/alloc.c b/kmod/src/alloc.c
index ac9601b8..1adbcd37 100644
--- a/kmod/src/alloc.c
+++ b/kmod/src/alloc.c
@@ -261,20 +261,17 @@ static bool invalid_extent(u64 start, u64 end, u64 first, u64 last)
 
 static bool invalid_meta_blkno(struct super_block *sb, u64 blkno)
 {
-	struct scoutfs_super_block *super = &SCOUTFS_SB(sb)->super;
+	struct scoutfs_sb_info *sbi = SCOUTFS_SB(sb);
+	u64 last_meta = (i_size_read(sbi->meta_bdev->bd_inode) >> SCOUTFS_BLOCK_LG_SHIFT) - 1;
 
-	return invalid_extent(blkno, blkno,
-			      le64_to_cpu(super->first_meta_blkno),
-			      le64_to_cpu(super->last_meta_blkno));
+	return invalid_extent(blkno, blkno, SCOUTFS_META_DEV_START_BLKNO, last_meta);
 }
 
 static bool invalid_data_extent(struct super_block *sb, u64 start, u64 len)
 {
-	struct scoutfs_super_block *super = &SCOUTFS_SB(sb)->super;
+	u64 last_data = (i_size_read(sb->s_bdev->bd_inode) >> SCOUTFS_BLOCK_SM_SHIFT) - 1;
 
-	return invalid_extent(start, start + len - 1,
-			      le64_to_cpu(super->first_data_blkno),
-			      le64_to_cpu(super->last_data_blkno));
+	return invalid_extent(start, start + len - 1, SCOUTFS_DATA_DEV_START_BLKNO, last_data);
 }
 
 void scoutfs_alloc_init(struct scoutfs_alloc *alloc,
diff --git a/kmod/src/format.h b/kmod/src/format.h
index fb6c1f4f..39fdddd2 100644
--- a/kmod/src/format.h
+++ b/kmod/src/format.h
@@ -779,11 +779,7 @@ struct scoutfs_super_block {
 	__le64 seq;
 	__le64 next_ino;
 	__le64 total_meta_blocks;	/* both static and dynamic */
-	__le64 first_meta_blkno;	/* first dynamically allocated */
-	__le64 last_meta_blkno;
 	__le64 total_data_blocks;
-	__le64 first_data_blkno;
-	__le64 last_data_blkno;
 	struct scoutfs_quorum_config qconf;
 	struct scoutfs_alloc_root meta_alloc[2];
 	struct scoutfs_alloc_root data_alloc;
diff --git a/kmod/src/super.c b/kmod/src/super.c
index 3d2b3133..eccc6023 100644
--- a/kmod/src/super.c
+++ b/kmod/src/super.c
@@ -336,28 +336,16 @@ int scoutfs_write_super(struct super_block *sb,
 				      sizeof(struct scoutfs_super_block));
 }
 
-static bool invalid_blkno_limits(struct super_block *sb, char *which,
-				 u64 start, __le64 first, __le64 last,
-				 struct block_device *bdev, int shift)
+static bool small_bdev(struct super_block *sb, char *which, u64 blocks,
+		       struct block_device *bdev, int shift)
 {
-	u64 blkno;
+	u64 size = (u64)i_size_read(bdev->bd_inode);
+	u64 count = size >> shift;
 
-	if (le64_to_cpu(first) < start) {
-		scoutfs_err(sb, "super block first %s blkno %llu is within first valid blkno %llu",
-			which, le64_to_cpu(first), start);
-		return true;
-	}
+	if (blocks > count) {
+		scoutfs_err(sb, "super block records %llu %s blocks, but device %u:%u size %llu only allows %llu blocks",
+			blocks, which, MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev), size, count);
 
-	if (le64_to_cpu(first) > le64_to_cpu(last)) {
-		scoutfs_err(sb, "super block first %s blkno %llu is greater than last %s blkno %llu",
-			which, le64_to_cpu(first), which, le64_to_cpu(last));
-		return true;
-	}
-
-	blkno = (i_size_read(bdev->bd_inode) >> shift) - 1;
-	if (le64_to_cpu(last) > blkno) {
-		scoutfs_err(sb, "super block last %s blkno %llu is beyond device size last blkno %llu",
-			which, le64_to_cpu(last), blkno);
 		return true;
 	}
 
@@ -417,16 +405,10 @@ static int scoutfs_read_super_from_bdev(struct super_block *sb,
 
 	/* XXX do we want more rigorous invalid super checking? */
 
-	if (invalid_blkno_limits(sb, "meta",
-			         SCOUTFS_META_DEV_START_BLKNO,
-				 super->first_meta_blkno,
-				 super->last_meta_blkno, sbi->meta_bdev,
-				 SCOUTFS_BLOCK_LG_SHIFT) ||
-	    invalid_blkno_limits(sb, "data",
-			         SCOUTFS_DATA_DEV_START_BLKNO,
-				 super->first_data_blkno,
-				 super->last_data_blkno, sb->s_bdev,
-				 SCOUTFS_BLOCK_SM_SHIFT)) {
+	if (small_bdev(sb, "metadata", le64_to_cpu(super->total_meta_blocks), sbi->meta_bdev,
+		       SCOUTFS_BLOCK_LG_SHIFT) ||
+	    small_bdev(sb, "data", le64_to_cpu(super->total_data_blocks), sb->s_bdev,
+		       SCOUTFS_BLOCK_SM_SHIFT)) {
 		ret = -EINVAL;
 	}
 
diff --git a/utils/src/mkfs.c b/utils/src/mkfs.c
index e18d5f9b..23df0071 100644
--- a/utils/src/mkfs.c
+++ b/utils/src/mkfs.c
@@ -241,11 +241,7 @@ static int do_mkfs(struct mkfs_args *args)
 	super->next_ino = cpu_to_le64(SCOUTFS_ROOT_INO + 1);
 	super->seq = cpu_to_le64(1);
 	super->total_meta_blocks = cpu_to_le64(last_meta + 1);
-	super->first_meta_blkno = cpu_to_le64(next_meta);
-	super->last_meta_blkno = cpu_to_le64(last_meta);
 	super->total_data_blocks = cpu_to_le64(last_data - first_data + 1);
-	super->first_data_blkno = cpu_to_le64(first_data);
-	super->last_data_blkno = cpu_to_le64(last_data);
 
 	assert(sizeof(args->slots) ==
 		     member_sizeof(struct scoutfs_super_block, qconf.slots));
diff --git a/utils/src/print.c b/utils/src/print.c
index 4c79a5fb..920393f3 100644
--- a/utils/src/print.c
+++ b/utils/src/print.c
@@ -951,8 +951,7 @@ static void print_super_block(struct scoutfs_super_block *super, u64 blkno)
 
 	/* XXX these are all in a crazy order */
 	printf("  next_ino %llu seq %llu\n"
-	       "  total_meta_blocks %llu first_meta_blkno %llu last_meta_blkno %llu\n"
-	       "  total_data_blocks %llu first_data_blkno %llu last_data_blkno %llu\n"
+	       "  total_meta_blocks %llu total_data_blocks %llu\n"
 	       "  meta_alloc[0]: "ALCROOT_F"\n"
 	       "  meta_alloc[1]: "ALCROOT_F"\n"
 	       "  data_alloc: "ALCROOT_F"\n"
@@ -969,11 +968,7 @@ static void print_super_block(struct scoutfs_super_block *super, u64 blkno)
 		le64_to_cpu(super->next_ino),
 		le64_to_cpu(super->seq),
 		le64_to_cpu(super->total_meta_blocks),
-		le64_to_cpu(super->first_meta_blkno),
-		le64_to_cpu(super->last_meta_blkno),
 		le64_to_cpu(super->total_data_blocks),
-		le64_to_cpu(super->first_data_blkno),
-		le64_to_cpu(super->last_data_blkno),
 		ALCROOT_A(&super->meta_alloc[0]),
 		ALCROOT_A(&super->meta_alloc[1]),
 		ALCROOT_A(&super->data_alloc),