FreeBSD 10.1-stable: repeatable panic when trying to copy files from an ext3 filesystem mounted read-only

[Torfinn Ingolfsen]

Hello,
I get a repeatable panic when trying to cpy files from an ext3 filesystewm which is mounted read-only. Listing files works ok.
Details:
root at kg-u35jc# uname -a
FreeBSD kg-u35jc.kg4.no 10.1-STABLE FreeBSD 10.1-STABLE #0 r283269: Fri May 22 09:14:57 CEST 2015
     root at kg-u35jc.kg4.no:/usr/obj/usr/src/sys/GENERIC  amd64

Steps to reproduce:
# kldload ext2fs
# mount -r -t ext2fs /dev/ada0s5 /mnt
# cp /mnt/whatever-file <somedir>

Results in a nice panic:
root at kg-u35jc# cat /var/crash/info.0
Dump header from device /dev/ada0s3b
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 1075154944B (1025 MB)
  Blocksize: 512
  Dumptime: Mon May 25 20:07:55 2015
  Hostname: kg-u35jc.kg4.no
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 10.1-STABLE #0 r283269: Fri May 22 09:14:57 CEST 2015
    root at kg-u35jc.kg4.no:/usr/obj/usr/src/sys/GENERIC
  Panic String: __lockmgr_args: recursing on non recursive lockmgr getblk @ (null):0

  Dump Parity: 3531684913
  Bounds: 0
  Dump Status: good

which is easy to reproduce:
root at kg-u35jc# cat /var/crash/info.1
Dump header from device /dev/ada0s3b
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 478572544B (456 MB)
  Blocksize: 512
  Dumptime: Mon May 25 20:24:29 2015
  Hostname: kg-u35jc.kg4.no
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 10.1-STABLE #0 r283269: Fri May 22 09:14:57 CEST 2015
    root at kg-u35jc.kg4.no:/usr/obj/usr/src/sys/GENERIC
  Panic String: __lockmgr_args: recursing on non recursive lockmgr getblk @ (null):0

  Dump Parity: 4100829037
  Bounds: 1
  Dump Status: good

Is this a known problem ( I tried searching, but didn't find anything), or should I put it into Bugzilla?
(core.txt.[01] are available, but largish at over 200K each, so I didn't try to get the mailing list to accept them)
-- 
Torfinn Ingolfsen <torfinn.ingolfsen at getmail.no>