assertion "bp->b_bcount <= todo" failed

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
on a netbsd-6 host, I got this:
panic: kernel diagnostic assertion "bp->b_bcount <= todo" failed: file "/home/bouyer/src-6/src/sys/kern/kern_physio.c", line 176 
cpu14: Begin traceback...
kern_assert() at netbsd:kern_assert+0x48
physio_biodone() at netbsd:physio_biodone+0xe6
biodone2() at netbsd:biodone2+0x8d
dkiodone() at netbsd:dkiodone+0x84
biodone2() at netbsd:biodone2+0x8d
bdev_strategy() at netbsd:bdev_strategy+0x47
spec_strategy() at netbsd:spec_strategy+0x3b
VOP_STRATEGY() at netbsd:VOP_STRATEGY+0x33
dkstart() at netbsd:dkstart+0x2f
dkstrategy() at netbsd:dkstrategy+0xd6
physio() at netbsd:physio+0x24f
cdev_read() at netbsd:cdev_read+0x5d
spec_read() at netbsd:spec_read+0x1cd
VOP_READ() at netbsd:VOP_READ+0x37
vn_read() at netbsd:vn_read+0xa0
dofileread() at netbsd:dofileread+0x71
sys_read() at netbsd:sys_read+0x62
syscall() at netbsd:syscall+0xc4

this was while running dump(8) from amanda. I've seen it twice, but
there has been more than one year between the two panics, and amanda runs
every night.

Does this ring a bell to someone ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--