Re: Xfs lockdep warning with for-dave-for-4.6 branch

[Dave Chinner <david@fromorbit.com>]

[resend with the xfs list corrected.]

On Thu, Oct 06, 2016 at 03:04:54PM +0200, Michal Hocko wrote:
> [Let me ressurect this thread]
> 
> On Wed 01-06-16 20:16:17, Peter Zijlstra wrote:
> > On Wed, Jun 01, 2016 at 03:17:58PM +0200, Michal Hocko wrote:
> > > Thanks Dave for your detailed explanation again! Peter do you have any
> > > other idea how to deal with these situations other than opt out from
> > > lockdep reclaim machinery?
> > > 
> > > If not I would rather go with an annotation than a gfp flag to be honest
> > > but if you absolutely hate that approach then I will try to check wheter
> > > a CONFIG_LOCKDEP GFP_FOO doesn't break something else. Otherwise I would
> > > steal the description from Dave's email and repost my patch.
> > > 
> > > I plan to repost my scope gfp patches in few days and it would be good
> > > to have some mechanism to drop those GFP_NOFS to paper over lockdep
> > > false positives for that.
> > 
> > Right; sorry I got side-tracked in other things again.
> > 
> > So my favourite is the dedicated GFP flag, but if that's unpalatable for
> > the mm folks then something like the below might work. It should be
> > similar in effect to your proposal, except its more limited in scope.
> 
> OK, so the situation with the GFP flags is somehow relieved after 
> http://lkml.kernel.org/r/20160912114852.GI14524@dhcp22.suse.cz and with
> the root radix tree remaining the last user which mangles gfp_mask and
> tags together we have some few bits left there. As you apparently hate
> any scoped API and Dave thinks that per allocation flag is the only
> maintainable way for xfs what do you think about the following?

It's a workable solution to allow XFS to play whack-a-mole games
with lockdep again. As to the implementation - that's for other
people to decide....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com