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
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