Re: 2.6.17-rc5-mm3-lockdep - locking error in quotaon

[Ingo Molnar <mingo@elte.hu>]

* Jan Kara <jack@suse.cz> wrote:

> > but that doesn't quite match your description...
>   This piece of code is there just because we avoid page cache when
> doing quota writes. That is a different story and should cause problems
> with your lock checker.
>   Standard way of running quota is:
> - get i_mutex for data_inode
> - write some data to data_inode
>   - requires allocation -> calls DQUOT_ALLOC_SPACE
>   - DQUOT_ALLOC_SPACE acquires some quota locks, decides it wants to
>     write out quota structure (e.g. because we are journaling quota and
>     must preserve quota integrity)
>     - acquires dqio_sem, calls filesystem specific quota writing
>       function - e.g. ext3_quota_write()
>     - this function acquires i_mutex for quota file
> 
> I think this is the type of circle your checker has found.

the validator noticed a circular dependency (AB->BA, or AB->BC->CA, 
etc.) - while the nesting above it would report as: "BUG: possible 
deadlock detected!".

	Ingo