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SubjectRe: ext3: slow symlink corruption on umount...
Arthur Jones wrote:
> On Thu, Oct 30, 2008 at 02:34:00PM -0700, Arthur Jones wrote:
>> Hi Eric, ...
>>
>> On Thu, Oct 30, 2008 at 11:03:49AM -0700, Eric Sandeen wrote:
>>> [...]
>>> Something is definitely racy here; in my simple testcase I get failures
>>> maybe 30-50% of the time...
>> Some more info: in the working case, the inodes are put
>> back on sb->s_dirty at then next ext3_sync_fs() call:
>>
>> __fsync_super -> DQUOT_SYNC -> ext3_sync_fs -> log_wait_commit
>>
>> In the failing case, journal_start_commit returns 0 in ext_sync_fs
>> and the inodes disappear into never-never land...
>
> More details, these are dumps at __log_start_commit in the
> call chain described above, the first column is the failing
> case, the next column is working case, t_expires is the delta
> from the time the dump was taken:
>
> journal->j_flags 0x10 0x10
> journal->j_tail_sequence 515 519
> journal->j_transaction_sequence 517 522
> journal->j_commit_sequence 514 519
> journal->j_commit_request 516 520
>
> journal->j_running_transaction->t_tid 516 521
> journal->j_running_transaction->t_state 0 0
> journal->j_running_transaction->t_updates 0 0
> journal->j_running_transaction->t_handle_count 27305 27344
> journal->j_running_transaction->t_expires -566 28
>
> Can you tell from this whether the transactions
> are messed up or whether we're just missing a
> wake_up? Any other info you'd like to see?

That's kind of along the lines of what I'm seeing; also, in particular,
I'm never seeing the buffer_head in question (the one for the block
which contains the slow link's data) transition from jbddirty to normal
BH_Dirty. I've had to take a break from this today, but will be back at
it a bit later... since I have a solid testcase I'm sure I'll get to the
bottom of it ... :) I'll probably hook up akpm's buffer tracing
infrastructure, just need to find a decent thing to trigger on to dump
out the history.

-Eric


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