Re: [PATCH 02/11] writeback: switch to per-bdi threads forflushing data

[Jan Kara]

On Wed 20-05-09 13:32:34, Jens Axboe wrote:
> On Wed, May 20 2009, Jan Kara wrote:
> >   Hi Jens,
> > 
> >   a few comments here. Mainly, I still don't think the sys_sync() is
> > working right - see comments below.
> 
> Thanks! I took the liberty of killing some of the code in between, to
> make it easier to see.
> 
> > > +void bdi_writeback_all(struct super_block *sb, long nr_pages)
> > > +{
> > > +	struct backing_dev_info *bdi;
> > > +
> > > +	rcu_read_lock();
> > > +
> > > +restart:
> > > +	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
> >   Isn't the RCU list here a bit overengineering? AFAICS we use the list
> > only here and if I'm grepping right, generic_sync_sb_inodes() is currently
> > only used for data integrity sync (after your patches) from fs-writeback.c
> > and by UBIFS to do equivalent of writeback_inodes(). So simple spinlock
> > guarding the list should be just fine. Or am I missing something?
> 
> Sure, we could. But it's really not that much of a difference,
> implementation wise.
  Yeah. It's just that when I see RCU, I'm a bit cautious what's going on.
When I see spinlock, everything is simple and clear ;). And I'm in favor of
using the simplest synchronization primitive that does it's work good
enough ;).

								Honza
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/