bg fsck and fs corruption

phk's sparc panicked while I was using it for package building, and
since he had forgotten to disable bg fsck I was reminded again of why
I turn it off on all my other systems:

twinsun# rm -rf old
rm: old/26422/usr/local/lib: Directory not empty
rm: old/26422/usr/local: Directory not empty
rm: old/26422/usr: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib/perl5/5.8.4/mach/auto/threads: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib/perl5/5.8.4/mach/auto: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib/perl5/5.8.4/mach: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib/perl5/5.8.4: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib/perl5: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf/lib: Directory not empty
rm: old/26422/var/tmp/instmp.laCtQf: Directory not empty
rm: old/26422/var/tmp: Directory not empty
rm: old/26422/var: Directory not empty
rm: old/26422: Directory not empty
rm: old: Directory not empty
twinsun# ls -l old/26422/usr/local/lib
total 0

bg fsck noticed the usual softdep problems, but did not report or fix
the corruption:

[...]
Jun 12 07:38:47 twinsun fsck: /dev/da1c: INCORRECT BLOCK COUNT I=4381849 (4 should be 0) (CORRECTED)
Jun 12 07:38:47 twinsun fsck: /dev/da1c: INCORRECT BLOCK COUNT I=4381850 (4 should be 0) (CORRECTED)
Jun 12 07:38:47 twinsun fsck: /dev/da1c: INCORRECT BLOCK COUNT I=4381853 (4 should be 0) (CORRECTED)
Jun 12 07:38:47 twinsun fsck:

Note the lack of summary line.  I don't know if it was trying to log
the more serious corruption but didn't because of a bug, or if it just
didn't detect it.

Kris