Re: 2.6.18 ext3 panic.

Badari Pulavarty
2006-10-12T21:55:26Z

Eric Sandeen wrote:
> Andrew Morton wrote:
>
>
>> On Thu, 12 Oct 2006 14:28:20 +0200
>> Jan Kara <jack@suse.cz> wrote:
>>
>>
>>
>>> Where can we call
>>> journal_dirty_data() without PageLock?
>>>
>>>
>> block_write_full_page() will unlock the page, so ext3_writepage()
>> will run journal_dirty_data_fn() against an unlocked page.
>>
>> I haven't looked into the exact details of the race, but it should
>> be addressable via jbd_lock_bh_state() or j_list_lock coverage
>>
> I'm testing with something like this now; seem sane?
>
> journal_dirty_data & journal_unmap_data both check do
> jbd_lock_bh_state(bh) close to the top... journal_dirty_data_fn has checked
> buffer_mapped before getting into journal_dirty_data, but that state may
> change before the lock is grabbed. Similarly re-check after we drop the lock.
>
>
This is exactly the solution I proposed earlier (to check
buffer_mapped() before calling submit_bh()).
But at that time, Jan pointed out that the whole handling is wrong.

But if this is the only case we need to handle, I am okay with this band
aid :)

Thanks,
Badari