Ocfs2 devel - May 2023 - [PATCH 2/2] ocfs2: add error handling path when jbd2 enter ABORT status

On Thu, May 04, 2023 at 05:41:29PM +0800, Joseph Qi
wrote:
> 
> 
> On 5/4/23 4:02 PM, Heming Zhao wrote:
> > On Thu, May 04, 2023 at 03:34:49PM +0800, Joseph Qi wrote:
> >>
> >>
> >> On 5/4/23 2:21 PM, Heming Zhao wrote:
> >>> On Thu, May 04, 2023 at 10:27:46AM +0800, Joseph Qi wrote:
> >>>>
> >>>>
> >>>> On 4/30/23 11:13 AM, Heming Zhao wrote:
> >>>>> fstest generic cases 347 361 628 629 trigger a same
issue:
> >>>>> When jbd2 enter ABORT status, ocfs2 ignores it and
keep going to commit
> >>>>> journal.
> >>>>
> >>>> What's the end user impact?
> >>>
> >>> There are two impacts:
> >>>
> >>> 1. this issue makes unmount command hanging.
> >>>
> >>> No one likes or accepts filesystem unmount failure when
underlying devices meets
> >>> error. For comparison, other FSs (e.g. ext4, xfs, gfs2, ..)
could do unmount
> >>> successfully.
> >>>
> >>
> >> So umount hang should be in the patch description, right?
> > 
> > OK.
> > 
> >>
> >>> 2. for developers to verify their patch doesn't make any
regression.
> >>>
> >>> fstest is a famious & important fs testsuite.
> >>> (Yes, I know ocfs2 has itself testsuite ocfs2_test.)
> >>>
> >>> Current status, there are many test cases (about 9 in my env)
cause fstest
> >>> hanging and blocking fstest to run. I did test for gfs2 on
latest tumbleweed,
> >>> gfs2 only has 1 hanging case.
> >>>
> >>> In my view, ocfs2 developers or maintainers at least make
ocfs2 to finish the
> >>> testsuite. Long-term target is to make ocfs2 to pass all the
testsuite.
> >>>
> >>> On kernel 6.2.9-1, the fstest 'quick' test group
result:
> >>> (the result based on my two patches [1/2] & [2/2])
> >>> ```
> >>> ./check -g quick -T -b -s ocfs2 -e generic/081 -e generic/648
> >>>
> >>> Failures: generic/003 generic/013 generic/015 generic/040
generic/041
> >>> generic/062 generic/082 generic/104 generic/107 generic/228
generic/244
> >>> generic/266 generic/272 generic/277 generic/281 generic/322
generic/329
> >>> generic/331 generic/336 generic/343 generic/376 generic/379
generic/380
> >>> generic/383 generic/384 generic/385 generic/386 generic/400
generic/410
> >>> generic/424 generic/441 generic/448 generic/449 generic/471
generic/479
> >>> generic/493 generic/495 generic/510 generic/537 generic/552
generic/563
> >>> generic/578 generic/594 generic/607 generic/620 generic/628
generic/630
> >>> generic/636 generic/702
> >>> Failed 49 of 568 tests
> >>> ```
> >>>
> >>>>
> >>>> JBD2_ABORT indicates a fatal error happens, either in
jounral layer or
> >>>> filesystem. And we should not commit any further
transactions.
> >>>> It seems that we may unify the behavior like:
> >>>>
> >>>> if (is_journal_aborted(journal))
> >>>> 	return -EROFS;
> >>>>
> >>>>
> >>> IIUC, do you mean add above code in ocfs2_commit_cache or in
> >>> ocfs2_commit_thread?
> >>
> >> Yes, break the loop in ocfs2_commit_thread() in case of journal
abort.
> >> Actually we've handled this case before, but just limit the
print. But
> >> it seems not enough now.
> > 
> > I wrote in my previous mail. Follow your idea, The code should be:
> > 
> > if (is_journal_aborted(journal)) {
> > 	ocfs2_error(osb->sb, "jbd2 status: ABORT.\n"); //this
line is important.
> > 	return -EROFS;
> > }
> > 
> > Only return -EROFS then break loop in ocfs2_commit_thread() is not
enough.
> > Without ocfs2_error(), ocfs2 could accept new IOs from userspace, then
the new
> > IOs will trigger IO error then trigger RO status. This flow is wrong,
we should
> > mark RO as early as possible when JBD ABORT happens. In my view, the
best place
> > is my [2/2] patch code which in ocfs2_commit_cache().
> > 
> 
> Agree, but ocfs2_abort() is more appropriate here, see
> ocfs2_start_trans(). But ocfs2_abort() may panic system, I'm afraid it
> has to change to read-only accordingly.
You are right. I ever used ocfs2_abort() then got panic. :)
So I changed to ocfs2_error(). I also sent two mails in 2023-4-30 (the first
mail has mess format by thunderbird). I copy the mail content here:
```
More info for this patch, maybe I should write below info in commit log.
>From the comment of __ocfs2_abort(), there is another way to handle
journal ABORT: panic.
And fstest generic test NO. 648 will trigger ocfs2_abort then make
kernel panic. I don't like the panic style, ocfs2 should elegantly
handle journal abnormal case.
```

fstest NO. 648 could trigger ocfs2_abort from ocfs2_start_trans(). So you could
find my previous mail, I ran the fstest with parameter '-e generic/648',
which
means fstest excludes NO. 648.

The only different between ocfs2_abort and ocfs2_error is set
OCFS2_MOUNT_ERRORS_PANIC, which could trigger panic. If you think panic is
brute, I suggest to use ocfs2_error.
> 
> >> BTW, the basic rule here is, we don't want to change journal
to prevent
> >> other nodes corrupting the filesystem.
> > 
> > If my memory is correct, every node has itself special journal
partition.
> > If the HA stack assigns the same (before fenced) nodeid to JBD ABORTed
machine,
> > No other node could corrupting the fs.
> > 
> I don't think it's a good idea to modify journal even flush fails.
Why
> not catch EROFS in commit thread and break? Now we can only expect
> umount continues with error, right?
> 
With your idea, I spent more than two hours for coding & testing. The result
is
my patch [2/2] is correct. Please believe my patch [2/2].

In patch [2/2], there is 'goto reset' which will resolve below three
issues:

ocfs2_commit_cache
 + ... ...
reset:  //goto label
 + ocfs2_inc_trans_id(journal); //<1.1>
 + atomic_set(&journal->j_num_trans, 0); //<2>
 + ocfs2_wake_downconvert_thread(osb); //<3>
 + wake_up(&journal->j_checkpointed); //<1.2>
 
1> trigger hanging

umount
 ... ...
  ocfs2_clear_inode
   ocfs2_checkpoint_inode(inode)
    + ocfs2_ci_fully_checkpointed() //1.1: check '->j_trans_id'
    + wait_event(osb->journal->j_checkpointed, ...)
       + 1.2: will wait forever, if commit thread exits.

2> trigger BUG_ON()

ocfs2_journal_shutdown
 + BUG_ON(atomic_read(&(osb->journal->j_num_trans)) != 0);

3> trigger dlm lock convert blocking

if there is pending downconvert lock, no one kick it.

At last, you could set up a fstest env and verify my writing.

- Heming

On 5/5/23 12:20 AM, Heming Zhao wrote:
> On Thu, May 04, 2023 at 05:41:29PM +0800, Joseph Qi wrote:
>>
>>
>> On 5/4/23 4:02 PM, Heming Zhao wrote:
>>> On Thu, May 04, 2023 at 03:34:49PM +0800, Joseph Qi wrote:
>>>>
>>>>
>>>> On 5/4/23 2:21 PM, Heming Zhao wrote:
>>>>> On Thu, May 04, 2023 at 10:27:46AM +0800, Joseph Qi wrote:
>>>>>>
>>>>>>
>>>>>> On 4/30/23 11:13 AM, Heming Zhao wrote:
>>>>>>> fstest generic cases 347 361 628 629 trigger a same
issue:
>>>>>>> When jbd2 enter ABORT status, ocfs2 ignores it and
keep going to commit
>>>>>>> journal.
>>>>>>
>>>>>> What's the end user impact?
>>>>>
>>>>> There are two impacts:
>>>>>
>>>>> 1. this issue makes unmount command hanging.
>>>>>
>>>>> No one likes or accepts filesystem unmount failure when
underlying devices meets
>>>>> error. For comparison, other FSs (e.g. ext4, xfs, gfs2, ..)
could do unmount
>>>>> successfully.
>>>>>
>>>>
>>>> So umount hang should be in the patch description, right?
>>>
>>> OK.
>>>
>>>>
>>>>> 2. for developers to verify their patch doesn't make
any regression.
>>>>>
>>>>> fstest is a famious & important fs testsuite.
>>>>> (Yes, I know ocfs2 has itself testsuite ocfs2_test.)
>>>>>
>>>>> Current status, there are many test cases (about 9 in my
env) cause fstest
>>>>> hanging and blocking fstest to run. I did test for gfs2 on
latest tumbleweed,
>>>>> gfs2 only has 1 hanging case.
>>>>>
>>>>> In my view, ocfs2 developers or maintainers at least make
ocfs2 to finish the
>>>>> testsuite. Long-term target is to make ocfs2 to pass all
the testsuite.
>>>>>
>>>>> On kernel 6.2.9-1, the fstest 'quick' test group
result:
>>>>> (the result based on my two patches [1/2] & [2/2])
>>>>> ```
>>>>> ./check -g quick -T -b -s ocfs2 -e generic/081 -e
generic/648
>>>>>
>>>>> Failures: generic/003 generic/013 generic/015 generic/040
generic/041
>>>>> generic/062 generic/082 generic/104 generic/107 generic/228
generic/244
>>>>> generic/266 generic/272 generic/277 generic/281 generic/322
generic/329
>>>>> generic/331 generic/336 generic/343 generic/376 generic/379
generic/380
>>>>> generic/383 generic/384 generic/385 generic/386 generic/400
generic/410
>>>>> generic/424 generic/441 generic/448 generic/449 generic/471
generic/479
>>>>> generic/493 generic/495 generic/510 generic/537 generic/552
generic/563
>>>>> generic/578 generic/594 generic/607 generic/620 generic/628
generic/630
>>>>> generic/636 generic/702
>>>>> Failed 49 of 568 tests
>>>>> ```
>>>>>
>>>>>>
>>>>>> JBD2_ABORT indicates a fatal error happens, either in
jounral layer or
>>>>>> filesystem. And we should not commit any further
transactions.
>>>>>> It seems that we may unify the behavior like:
>>>>>>
>>>>>> if (is_journal_aborted(journal))
>>>>>> 	return -EROFS;
>>>>>>
>>>>>>
>>>>> IIUC, do you mean add above code in ocfs2_commit_cache or
in
>>>>> ocfs2_commit_thread?
>>>>
>>>> Yes, break the loop in ocfs2_commit_thread() in case of journal
abort.
>>>> Actually we've handled this case before, but just limit the
print. But
>>>> it seems not enough now.
>>>
>>> I wrote in my previous mail. Follow your idea, The code should be:
>>>
>>> if (is_journal_aborted(journal)) {
>>> 	ocfs2_error(osb->sb, "jbd2 status: ABORT.\n"); //this
line is important.
>>> 	return -EROFS;
>>> }
>>>
>>> Only return -EROFS then break loop in ocfs2_commit_thread() is not
enough.
>>> Without ocfs2_error(), ocfs2 could accept new IOs from userspace,
then the new
>>> IOs will trigger IO error then trigger RO status. This flow is
wrong, we should
>>> mark RO as early as possible when JBD ABORT happens. In my view,
the best place
>>> is my [2/2] patch code which in ocfs2_commit_cache().
>>>
>>
>> Agree, but ocfs2_abort() is more appropriate here, see
>> ocfs2_start_trans(). But ocfs2_abort() may panic system, I'm afraid
it
>> has to change to read-only accordingly.
> 
> You are right. I ever used ocfs2_abort() then got panic. :)
> So I changed to ocfs2_error(). I also sent two mails in 2023-4-30 (the
first
> mail has mess format by thunderbird). I copy the mail content here:
> ```
> More info for this patch, maybe I should write below info in commit log.
> 
> From the comment of __ocfs2_abort(), there is another way to handle
> journal ABORT: panic.
> And fstest generic test NO. 648 will trigger ocfs2_abort then make
> kernel panic. I don't like the panic style, ocfs2 should elegantly
> handle journal abnormal case.
> ```
> 
> fstest NO. 648 could trigger ocfs2_abort from ocfs2_start_trans(). So you
could
> find my previous mail, I ran the fstest with parameter '-e
generic/648', which
> means fstest excludes NO. 648.
> 
> The only different between ocfs2_abort and ocfs2_error is set
> OCFS2_MOUNT_ERRORS_PANIC, which could trigger panic. If you think panic is
> brute, I suggest to use ocfs2_error.
> 
Looked back the history, it is designed to panic in cluster mode:
a2f2ddbf2baf ocfs2: __ocfs2_abort() should not enable panic for local mounts
>>
>>>> BTW, the basic rule here is, we don't want to change
journal to prevent
>>>> other nodes corrupting the filesystem.
>>>
>>> If my memory is correct, every node has itself special journal
partition.
>>> If the HA stack assigns the same (before fenced) nodeid to JBD
ABORTed machine,
>>> No other node could corrupting the fs.
>>>
>> I don't think it's a good idea to modify journal even flush
fails. Why
>> not catch EROFS in commit thread and break? Now we can only expect
>> umount continues with error, right?
>>
> 
> With your idea, I spent more than two hours for coding & testing. The
result is
> my patch [2/2] is correct. Please believe my patch [2/2].
> 
I am not arguing if your patch can pass the testcases above. I am
talking about whether we do it this way is right.

Now journal flush actually fails since journal is abort, which means
journal data are not reflected in filesystem. But after your change, it
behaves like we've done a normal checkpoint.

Take the following scenario into consideration:
N0 does some changes on file1, but now disk down and journal is abort,
and checkpoint behaves successfully even it does nothing.
N1 get the access right on file1 and does other changes, and checkpoint
normally.
N0 is crash, and N1 begins to recover N0, then data corruption happens.

I've fixed a similar issue in the past:
6f6a6fda2945 jbd2: fix ocfs2 corrupt when updating journal superblock fails

Thanks,
Joseph