invalid wire count-panic on invalid media

[Volker Stolz]

This crash was caused while copying from a zonked floppy to NFS.
Should a read error really be able to cause this?

FreeBSD menelaos.informatik.rwth-aachen.de 4.9-STABLE FreeBSD 4.9-STABLE #12: Mon Dec  8 15:14:27 CET 2003     root at menelaos.informatik.rwth-aachen.de:/usr/obj/usr/src/sys/MENELAOS  i386

IdlePTD at physical address 0x0042f000
initial pcb at physical address 0x0035dbc0
panicstr: vm_page_free: invalid wire count (4), pindex: 0x3
panic messages:
---
panic: vm_page_free: invalid wire count (4), pindex: 0x3
                                                                                                                             
syncing disks... 67 13 11 11 11 11 11 11 11 11 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
giving up on 1 buffers
Uptime: 6d15h42m23s
                                                                                                                             
dumping to dev #ad/0x20001, offset 2065696
dump ata0: resetting devices .. done
1023..0
---
#0  0xc017f152 in dumpsys ()
(kgdb) bt
#0  0xc017f152 in dumpsys ()
#1  0xc017ef1c in boot ()
#2  0xc017f350 in poweroff_wait ()
#3  0xc0284e1f in vm_page_free_toq ()
#4  0xc027ccf1 in vm_fault ()
#5  0xc02caa8f in trap_pfault ()
#6  0xc02ca6df in trap ()
#7  0xc02c96d1 in generic_copyin ()
#8  0xc0221c95 in nfs_write ()
#9  0xc01b590e in vn_write ()
#10 0xc018e972 in dofilewrite ()
#11 0xc018e823 in write ()
#12 0xc02cb0f5 in syscall2 ()
#13 0xc02bc475 in Xint0x80_syscall ()
#14 0x8048aa5 in ?? ()
#15 0x8048566 in ?? ()
#16 0x804813e in ?? ()