Re: Delayed allocation and page_lock vs transaction start ordering

[Jan Kara <jack@suse.cz>]

On Fri 18-04-08 12:54:47, Andreas Dilger wrote:
> On Apr 16, 2008  11:38 +0200, Jan Kara wrote:
> > On Tue 15-04-08 11:08:52, Mingming Cao wrote:
> > > I guess this reserve locking ordering allows support writepages() for
> > > ext3/4? What other the benefits?
> >
> >   Yes, that is one advantage. The other one (which I care about the most)
> > is that transaction commit code can take page_lock in the new locking order
> > which is necessary for the new ordered mode rewrite.
> 
> My understanding is that the main reason for the ordered mode rewrite is
> specifically to allow delalloc to still support ordered mode semantics.
> If the lock ordering is changed, and the jbd ordered mode is changed, but
> we don't support that with delalloc then we will have made a lot of changes
> (and likely introduced some bugs) with little benefit.
  Yes, with ordered mode rewrite, handling of data=ordered,delalloc is
going to be much simpler. But not that it would be my main motivation...

									Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR