kern/60834: LFS rollforward generates minor fsck_lfs error

["clare%csel.org@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60834
>Category:       kern
>Synopsis:       LFS rollforward generates minor fsck_lfs error
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 01 14:25:02 +0000 2026
>Originator:     Shinichi Doyashiki
>Release:        11.99.8 around 2026-09-28 04:00 JST
>Organization:
at home
>Environment:
NetBSD kanade2.hq.csel.org 11.99.8 NetBSD 11.99.8 (KANADE2_12) #27: Mon Sep 28 04:34:19 JST 2026  clare%kanade2.hq.csel.org@localhost:/export/netbsd/debuglfs/src/sys/arch/amd64/compile/KANADE2_12 amd64

>Description:
LFS rollforward generates minor fsck_lfs error

# sh preptest1.sh
dd: /dev/rdk4: end of device
33+0 records in
32+0 records out
33554432 bytes transferred in 2.173 secs (15441524 bytes/sec)
Creating a version 2 LFS32 with roll-forward ident 0xae448f62
32.0MB in 1023 segments of size 32768
super-block backups (for fsck -b #) at:
16, 6528, 13056, 19584, 26112, 32640, 39168, 45696, 52224, 58752.
1+0 records in
1+0 records out
1048576 bytes transferred in 0.008 secs (131072000 bytes/sec)
===> saving image
32+0 records in
32+0 records out
33554432 bytes transferred in 2.823 secs (11886089 bytes/sec)
===> restore image
32+0 records in
32+0 records out
33554432 bytes transferred in 1.448 secs (23172950 bytes/sec)
===> check before roll-forward
** /dev/rdk4 (NO WRITE)
** Last Mounted on 
** Phase 0 - Check Inode Free List
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Segment Block Accounting
2 files, 57 used, 58703 free
===> test roll-forward
===> check after roll-forward
** /dev/rdk4 (NO WRITE)
** File system is already clean
** Last Mounted on /testlfs
** Phase 0 - Check Inode Free List
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Segment Block Accounting
AVAIL GIVEN AS 61950, SHOULD BE 61948

FIX? no

2 files, 57 used, 58701 free
32+0 records in
32+0 records out
33554432 bytes transferred in 2.880 secs (11650844 bytes/sec)


>How-To-Repeat:
# cat /preptest1.sh 
#!/bin/sh
#
# LFS rollforward test
#
# create 32MB of LFS patition before use of this script
DISK=/dev/dk4
RDISK=/dev/rdk4

dd if=/dev/zero of=$RDISK bs=1m
newfs_lfs $RDISK
mkdir -p /testlfs
mount_lfs -n $DISK /testlfs
cd /testlfs
for i in 1; do
  dd if=/dev/zero of=testfile$$i.bin bs=1m count=1
done
rm testfile*.bin
cd /
# save image for later use
echo "===> saving image"
dd if=$RDISK of=/testlfs1.dmp bs=1m
sync
umount /testlfs
echo "===> restore image"
dd if=/testlfs1.dmp of=$RDISK bs=1m
echo "===> check before roll-forward"
fsck_lfs -nf $RDISK
echo "===> test roll-forward"
mount_lfs -n $DISK /testlfs
umount /testlfs
echo "===> check after roll-forward"
fsck_lfs -nf $RDISK
dd if=$RDISK of=/testlfs2.dmp bs=1m

>Fix:
unknown