resize_ffs isn't resizing

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

Based on:
xbd0: 30720 MB, 512 bytes/sect x 62914560 sectors

I have the following wedges:

/dev/rxbd0: 3 wedges:
dk0: 049c7554-3013-4f2f-a0a4-e8af4ebf3887, 262144 blocks at 64, type: msdos
dk1: root, 60563392 blocks at 262208, type: ffs
dk2: swap, 2088927 blocks at 60825600, type: swap

From the following GPT:
     start      size  index  contents
         0         1         PMBR
         1         1         Pri GPT header
         2        32         Pri GPT table
        34        30         Unused
        64    262144      1  GPT part - EFI System
    262208  60563392      2  GPT part - NetBSD FFSv1/FFSv2
  60825600   2088927      3  GPT part - NetBSD swap
  62914527        32         Sec GPT table
  62914559         1         Sec GPT header

dumpfs says:
ncg	163	size	15140848	blocks	14677886
bsize	16384	shift	14	mask	0xffffc000
fsize	2048	shift	11	mask	0xfffff800

I have then resized the underlying device so that it is:
xbd0: 40960 MB, 512 bytes/sect x 83886080 sectors

For the moment I have deleted the swap wedge and resized the gpt and the 
partition so that I have:
/dev/rxbd0: 2 wedges:
dk0: 049c7554-3013-4f2f-a0a4-e8af4ebf3887, 262144 blocks at 64, type: msdos
dk1: root, 80563392 blocks at 262208, type: ffs

From:
     start      size  index  contents
         0         1         PMBR
         1         1         Pri GPT header
         2        32         Pri GPT table
        34        30         Unused
        64    262144      1  GPT part - EFI System
    262208  80563392      2  GPT part - NetBSD FFSv1/FFSv2
  80825600   3060447         Unused
  83886047        32         Sec GPT table
  83886079         1         Sec GPT header

Now to resize the filesystem:
# resize_ffs -vy /dev/rdk1
Growing fs from 15140848 blocks to 20140848 blocks

Why 20140848, not 80563392? Even if I specify 80563392 with -s, it still only grows to 20140848.

dumpfs concurs:
ncg     217     size    20140848        blocks  19524526
bsize   16384   shift   14      mask    0xffffc000
fsize   2048    shift   11      mask    0xfffff800

I don't gain any free space:
Filesystem      1K-blocks         Used        Avail %Cap Mounted on
root_device      29355772     29326868     -1438884 105% /

And at a reboot, if I run resize_ffs again it claims to be growing from 15140848 to 20140848 again, so appears to have done nothing.

--
Stephen