Re: ufs_dirbad: /mnt: bad dir ino 50626 at offset 0: mangled entry

On Fri, Oct 22, 2021 at 11:33:22AM -0400, mike tancsa wrote:
> On 10/22/2021 11:21 AM, Mark Johnston wrote:
> > On Fri, Oct 22, 2021 at 10:36:01AM -0400, mike tancsa wrote:
> >> After cycles of this, unmounts, mounts etc, I get
> >>
> >>
> >> panic: ufs_dirbad: /mnt: bad dir ino 50626 at offset 0: mangled entry
> >> cpuid = 1
> >> time = 1634912598
> >> KDB: stack backtrace:
> >> #0 0xffffffff80c77035 at kdb_backtrace+0x65
> >> #1 0xffffffff80c28a47 at vpanic+0x187
> >> #2 0xffffffff80c288b3 at panic+0x43
> >> #3 0xffffffff80f345f7 at ufs_lookup_ino+0xdc7
> >> #4 0xffffffff80ceae1d at vfs_cache_lookup+0xad
> >> #5 0xffffffff80cf872c at lookup+0x46c
> >> #6 0xffffffff80cf785c at namei+0x26c
> >> #7 0xffffffff80d1c979 at vn_open_cred+0x509
> >> #8 0xffffffff80d12a3e at kern_openat+0x26e
> >> #9 0xffffffff810b4d3c at amd64_syscall+0x10c
> >> #10 0xffffffff8108bdab at fast_syscall_common+0xf8
> >> Uptime: 4m48s
> >>
> >> I forced an fsck on reboot, and the file system is clean. I also deleted
> >> /mnt and recreated the directory and still get this issue.  Any idea
> >> what might be causing it or how I can better track it down ?
> > Is the VM image stored on ZFS?  Which kernel revision is the host running?
> 
> Hi,
> 
>      The VM is in an Ubuntu host / KVM (Linux ubuntu1 5.11.0-38-generic 
> #42-Ubuntu SMP Fri Sep 24 ) with the VM image stored on its local zfs 
> file system. Do you think its some strange interaction with the 
> hypervisor ? The FreeBSD guest VM is RELENG_13 as of this morning, 
> GENERIC kernel stable/13-d8359af5b

I was seeing similar unexpected UFS corruption in a VM that appears to
be the result of a ZFS regression on the host.  But said ZFS regression
is likely FreeBSD-specific and is also relatively new.