panic: vm_page_free_toq: freeing mapped page

Hi there,

I'm afraid something got broken in BIO/VFS since January, 19.  I'm
getting the following panic at system shutdown, after flushing
buffers, and then at fsck run.  I have to load a Jan 19 kernel to
be able to run fsck.  The panicing kernel, as well as userland,
were built last night.

This trace is from an fsck-time panic.

panic: vm_page_free_toq: freeing mapped page 0xc0db3920
...
#11 0xc04e0213 in panic (
    fmt=0xc067644c "vm_page_free_toq: freeing mapped page %p")
    at /usr/src/sys/kern/kern_shutdown.c:539
#12 0xc0603ab6 in vm_page_free_toq (m=0xc0db3920)
    at /usr/src/sys/vm/vm_page.c:1015
#13 0xc0603081 in vm_page_free (m=0xc0db3920) at /usr/src/sys/vm/vm_page.c:403
#14 0xc05286dd in vfs_vmio_release (bp=0xc6ff1768)
    at /usr/src/sys/kern/vfs_bio.c:1521
#15 0xc0527ecd in brelse (bp=0xc6ff1768) at /usr/src/sys/kern/vfs_bio.c:1307
#16 0xc05363ca in flushbuflist (bufv=0x12, flags=0, bo=0xc1f5d0b4, slpflag=0,
    slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1129
#17 0xc0535fc1 in bufobj_invalbuf (bo=0xc1f5d0b4, flags=0, td=0xc1da0680,
    slpflag=0, slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1006
#18 0xc05361c1 in vinvalbuf (vp=0xc1f5d000, flags=0, td=0xc1da0680, slpflag=0,
    slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1065
#19 0xc05e121d in ffs_reload (mp=0xc1e4e400, td=0xc1da0680)
    at /usr/src/sys/ufs/ffs/ffs_vfsops.c:553
#20 0xc05e0710 in ffs_mount (mp=0xc1e4e400, td=0xc1da0680)
    at /usr/src/sys/ufs/ffs/ffs_vfsops.c:252
#21 0xc0532fb7 in vfs_domount (td=0xc1da0680, fstype=0xc1e4c9e0 "ufs",
    fspath=0xc1e4e400 "", fsflags=331777, fsdata=0xc1e4c9b0)
    at /usr/src/sys/kern/vfs_mount.c:858
#22 0xc05328ac in vfs_donmount (td=0xc1da0680, fsflags=331777,
    fsoptions=0xcbde1ba8) at /usr/src/sys/kern/vfs_mount.c:611
#23 0xc0534c89 in kernel_mount (ma=0xc1e4c990, flags=331777) at pcpu.h:163
#24 0xc05e0d91 in ffs_cmount (ma=0xc1e4c990, data=0xc0c15000, flags=331777,
    td=0xc1da0680) at /usr/src/sys/ufs/ffs/ffs_vfsops.c:427
#25 0xc0532a9a in mount (td=0xc1da0680, uap=0xcbde1d04)
    at /usr/src/sys/kern/vfs_mount.c:689

At shutdown time, the trace looks similarly (got it on the screen only):

panic
vm_page_free_toq
vm_page_free
vfs_vmio_release
brelse
flushbuflist
bufobj_invalbuf
vinvalbuf
vgonel
vflush
ffs_flushfiles
ffs_unmount
dounmount
vfs_unmountall
boot
reboot

Yar