kern/55552: panic with union mount

[christos%zoulas.com@localhost]

	Note: There was a bad value `' for the field `Class'.
	It was set to the default value of `sw-bug'.

>Number:         55552
>Category:       kern
>Synopsis:       kernel panics with union mount
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 08 17:10:00 +0000 2020
>Originator:     Christos Zoulas
>Release:        NetBSD 9.99.69
>Organization:
	Atom Smashing, Inc.
>Environment:
System: NetBSD vmb1.astron.com 9.99.69 NetBSD 9.99.69 (GENERIC) #83: Sat Aug 8 08:25:00 EDT 2020 christos%vmb1.astron.com@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
panic: kernel diagnostic assertion "fstrans_held(vp->v_mount)" failed: file "/p/src/sys/ufs/ufs/ufs_vnops.c", line 1873 
cpu0: Begin traceback...
vpanic() at netbsd:vpanic+0x152
__x86_indirect_thunk_rax() at netbsd:__x86_indirect_thunk_rax
ufs_strategy() at netbsd:ufs_strategy+0x1dc
VOP_STRATEGY() at netbsd:VOP_STRATEGY+0x3c
bio_doread() at netbsd:bio_doread+0x98
bread() at netbsd:bread+0x18
ffs_bufrd() at netbsd:ffs_bufrd+0x152
ufs_readdir() at netbsd:ufs_readdir+0x13e
VOP_READDIR() at netbsd:VOP_READDIR+0x4c
vn_readdir() at netbsd:vn_readdir+0xe7
sys___getdents30() at netbsd:sys___getdents30+0x72
syscall() at netbsd:syscall+0x283
--- syscall (number 390) ---
netbsd:syscall+0x283:
cpu0: End traceback...
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip 0xffffffff80221a25 cs 0x8 rflags 0x202 cr2 0x79ed49b98000 ilevel 0 rsp 0xffffbb826d284b10
curlwp 0xffffe3c9b30ab680 pid 994.994 lowest kstack 0xffffbb826d2802c0
Stopped in pid 994.994 (sh) at	netbsd:breakpoint+0x5:	leave	
?
breakpoint() at netbsd:breakpoint+0x5
vpanic() at netbsd:vpanic+0x152
__x86_indirect_thunk_rax() at netbsd:__x86_indirect_thunk_rax
ufs_strategy() at netbsd:ufs_strategy+0x1dc
VOP_STRATEGY() at netbsd:VOP_STRATEGY+0x3c
bio_doread() at netbsd:bio_doread+0x98
bread() at netbsd:bread+0x18
ffs_bufrd() at netbsd:ffs_bufrd+0x152
ufs_readdir() at netbsd:ufs_readdir+0x13e
VOP_READDIR() at netbsd:VOP_READDIR+0x4c
vn_readdir() at netbsd:vn_readdir+0xe7
sys___getdents30() at netbsd:sys___getdents30+0x72
syscall() at netbsd:syscall+0x283
--- syscall (number 390) ---
netbsd:syscall+0x283:

dumping to dev 168,4 (offset=558567, size=8318787):
dump 
--------------------------------------------------------------
>How-To-Repeat:
	union mount and then list files
>Fix:
	please