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

[Michal Hocko <mhocko@kernel.org>]

[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?
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