Ocfs2 devel - Feb 2023 - report BUG: io_uring triggers umount error

I can reproduce this in my local VM.
I've traced ocfs2_dismount_volume and found that it hasn't been called.
So EBUSY is returned in VFS layer. I guess something wrong when doing
a copy with linked SQEs (normal copy seems no problem).

Thanks,
Joseph

On 2/24/23 8:32 AM, Heming Zhao wrote:
> Hello List,
> 
> I found a weird bug on ocfs2. I am busying with other jobs, if anyone have
time
> he/she could fix it. This bug is blocking fstest generic/013 test case, and
also
> blocking fstest to do later test cases.
> 
> How to trigger:
> ```
> git clone git://git.kernel.dk/liburing.git
> cd liburing
> make
> cd examples
> mount -t ocfs2 /dev/sda /mnt
> cp /etc/hosts /mnt/a
> ./link-cp /mnt/a /mnt/b
> umount /mnt
> ```
> 
> umount trigger error message:
> ```
> # umount /mnt 
> umount: /mnt: target is busy.
> ```
> 
> The umount error can only be triggered by liburing write operation.
> 
> Thanks,
> Heming

On 2/24/23 2:54 PM, Joseph Qi wrote:
> I can reproduce this in my local VM.
> I've traced ocfs2_dismount_volume and found that it hasn't been
called.
> So EBUSY is returned in VFS layer. I guess something wrong when doing
> a copy with linked SQEs (normal copy seems no problem).
> 
I am inclined to agree with you. I also test liburing examples apps
on ext4 partition, everything looks fine.

I used below bpftrace method, the retval is '3'.
  bpftrace -e 'kr:mnt_get_count{printf("%d\n", retval);}'

It responds to flow: path_umount() => do_umount => mnt_get_count (gets
'3')

Thanks,
Heming
> 
> On 2/24/23 8:32 AM, Heming Zhao wrote:
>> Hello List,
>>
>> I found a weird bug on ocfs2. I am busying with other jobs, if anyone
have time
>> he/she could fix it. This bug is blocking fstest generic/013 test case,
and also
>> blocking fstest to do later test cases.
>>
>> How to trigger:
>> ```
>> git clone git://git.kernel.dk/liburing.git
>> cd liburing
>> make
>> cd examples
>> mount -t ocfs2 /dev/sda /mnt
>> cp /etc/hosts /mnt/a
>> ./link-cp /mnt/a /mnt/b
>> umount /mnt
>> ```
>>
>> umount trigger error message:
>> ```
>> # umount /mnt
>> umount: /mnt: target is busy.
>> ```
>>
>> The umount error can only be triggered by liburing write operation.
>>
>> Thanks,
>> Heming