8.0 can't find/read label on da3 (7.2 OK)

This morning I source-upgraded our main server (i386) from 7.2-RELEASE
to this morning's RELENG_8_0.  FreeBSD 8.0 seems unable to discover the
filesystem on /dev/da3.  The earlier discs (da0, da1, da2) on that
controller are fine.

If I boot 7.2-RELEASE from a live CD, bsdlabel happily reads the /da3s1
label, I can fsck the da3s1d UFS filesystem, and I can mount the
filesystem.  If I boot 8.0, I lose the disc again.

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Hardware (from 8.0 dmesg)
--------------------------------
ahd2: <Adaptec 29320A Ultra320 SCSI adapter> port 0xc800-0xc8ff,0xc400-0xc4ff mem 0xfc8fe000-0xfc8fffff irq 24 at device 1.0 on pci4
ahd2: [ITHREAD]

da3 at ahd2 bus 0 target 3 lun 0
da3: <SEAGATE ST373455LC 0005> Fixed Direct Access SCSI-3 device 
da3: 40.000MB/s transfers (20.000MHz, offset 63, 16bit)
da3: Command Queueing enabled
da3: 70007MB (143374744 512 byte sectors: 255H 63S/T 8924C)

--------------------------------
Works - FreeBSD 7.2
--------------------------------
Fixit# uname -a
FreeBSD  7.2-RELEASE FreeBSD 7.2-RELEASE #0: Fri May  1 08:49:13 UTC 2009     root_at_walker.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386

Fixit# ls -l /dev/da3*
crw-r-----  1 root  operator    0, 113 Nov 21 20:54 /dev/da3
crw-r-----  1 root  operator    0, 122 Nov 21 20:54 /dev/da3c
crw-r-----  1 root  operator    0, 147 Nov 21 20:54 /dev/da3cs1
crw-r-----  1 root  operator    0, 167 Nov 21 20:54 /dev/da3cs1c
crw-r-----  1 root  operator    0, 168 Nov 21 20:54 /dev/da3cs1d
crw-r-----  1 root  operator    0, 123 Nov 21 20:54 /dev/da3d
crw-r-----  1 root  operator    0, 121 Nov 21 20:54 /dev/da3s1
crw-r-----  1 root  operator    0, 145 Nov 21 20:54 /dev/da3s1c
crw-r-----  1 root  operator    0, 146 Nov 21 20:54 /dev/da3s1d

Fixit# fdisk /dev/da3
******* Working on device /dev/da3 *******
parameters extracted from in-core disklabel are:
cylinders=8924 heads=255 sectors/track=63 (16065 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=8924 heads=255 sectors/track=63 (16065 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 63, size 143363997 (70001 Meg), flag 80 (active)
	beg: cyl 0/ head 1/ sector 1;
	end: cyl 731/ head 254/ sector 63
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>

Fixit# bsdlabel /dev/da3s1
# /dev/da3s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 143363997        0    unused        0     0         # "raw" part, don't edit
  d: 143363981       16    4.2BSD     2048 16384 28552 

Fixit# fsck -pt ufs /dev/da3s1d
fstab: /etc/fstab:0: No such file or directory
fstab: /etc/fstab:0: No such file or directory
/dev/da3s1d: FILE SYSTEM CLEAN; SKIPPING CHECKS
/dev/da3s1d: clean, 17904497 free (8193 frags, 2237038 blocks, 0.0% fragmentation)

--------------------------------
Broken - FreeBSD 8.0
--------------------------------
rwsrv03# uname -a
FreeBSD rwsrv03.mby.riverwillow.net.au 8.0-RELEASE FreeBSD 8.0-RELEASE #2: Sat Nov 21 13:32:10 AEDT 2009     root_at_rwsrv03.mby.riverwillow.net.au:/build/obj/usr/src/sys/RWSRV03  i386

rwsrv03# ls -l /dev/da3*
crw-r-----  1 root  operator    0, 110 Nov 21 21:07 /dev/da3
crw-r-----  1 root  operator    0, 118 Nov 21 21:07 /dev/da3d

rwsrv03# fdisk /dev/da3
******* Working on device /dev/da3 *******
parameters extracted from in-core disklabel are:
cylinders=8924 heads=255 sectors/track=63 (16065 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=8924 heads=255 sectors/track=63 (16065 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 63, size 143363997 (70001 Meg), flag 80 (active)
	beg: cyl 0/ head 1/ sector 1;
	end: cyl 731/ head 254/ sector 63
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>

rwsrv03# bsdlabel /dev/da3s1
bsdlabel: unable to get correct path for /dev/da3s1: No such file or directory

rwsrv03# bsdlabel /dev/da3
# /dev/da3:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 143374744        0    unused        0     0         # "raw" part, don't edit
  d: 143374728       16    unused        0     0       
--------------------------------
-- 
John Marshall