[Bug 230220] UFS: the freezing ioctl (i.e.UFSSUSPEND) causes panic or EBUSY

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230220

            Bug ID: 230220
           Summary: UFS: the freezing ioctl (i.e.UFSSUSPEND) causes panic
                    or EBUSY
           Product: Base System
           Version: CURRENT
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: decui at microsoft.com

I'm running a FreeBSD VM with "the latest 12-CURRENT code + the default
sys/amd64/conf/GENERIC" on Hyper-V. I can reproduce the panic issue every time
with the test program test-freeze-thaw.c, which will be attached shortly.

The test program is a simplified version of the file
contrib/hyperv/tools/hv_vss_daemon.c
(https://github.com/freebsd/freebsd/blob/master/contrib/hyperv/tools/hv_vss_daemon.c).


[root at decui-b12 ~]# gpart show
=>       63  104857537  da0  MBR  (50G)
         63          1       - free -  (512B)
         64  104857536    1  freebsd  [active]  (50G)

=>        0  104857536  da0s1  BSD  (50G)
          0   98566144      1  freebsd-ufs  (47G)
   98566144    5242880      2  freebsd-swap  (2.5G)
  103809024    1048512         - free -  (512M)

=>       63  266338241  da1  MBR  (127G)
         63       1985       - free -  (993K)
       2048  266334208    1  freebsd  (127G)
  266336256       2048       - free -  (1.0M)

=>       40  104857520  da2  GPT  (50G)
         40       2008       - free -  (1.0M)
       2048   41943040    1  freebsd-ufs  (20G)
   41945088   62912472       - free -  (30G)

[root at decui-b12 ~]# mount
/dev/da0s1a on / (ufs, local, journaled soft-updates)
devfs on /dev (devfs, local, multilabel)
/dev/da2p1 on /mnt (ufs, local, soft-updates)

[root at decui-b12 ~]# ./test-freeze-thaw

Now the kernel panics immediately: 

ogin: panic: devfs_set_cdevpriv failed
cpuid = 11
time = 1532998033
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0034027560
vpanic() at vpanic+0x1a3/frame 0xfffffe00340275c0
doadump() at doadump/frame 0xfffffe0034027640
ffs_susp_ioctl() at ffs_susp_ioctl+0x223/frame 0xfffffe00340276a0
devfs_ioctl() at devfs_ioctl+0xcb/frame 0xfffffe00340276f0
VOP_IOCTL_APV() at VOP_IOCTL_APV+0xd9/frame 0xfffffe0034027720
vn_ioctl() at vn_ioctl+0x124/frame 0xfffffe0034027830
devfs_ioctl_f() at devfs_ioctl_f+0x1f/frame 0xfffffe0034027850
kern_ioctl() at kern_ioctl+0x2b9/frame 0xfffffe00340278b0
sys_ioctl() at sys_ioctl+0x15e/frame 0xfffffe0034027980
amd64_syscall() at amd64_syscall+0x281/frame 0xfffffe0034027ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe0034027ab0
--- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x800413e0a, rsp =
0x7fffffffea98, rbp =                                                          
                                                    0x7fffffffeaf0 ---
KDB: enter: panic
[ thread pid 1262 tid 100280 ]
Stopped at      kdb_enter+0x3b: movq    $0,kdb_why

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