Re: 2.6.18 ext3 panic.

[Badari Pulavarty <pbadari@us.ibm.com>]

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

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