From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 19 Oct 2016 11:33:09 +1100 From: Dave Chinner Subject: Re: Xfs lockdep warning with for-dave-for-4.6 branch Message-ID: <20161019003309.GG23194@dastard> References: <20160516130519.GJ23146@dhcp22.suse.cz> <20160516132541.GP3193@twins.programming.kicks-ass.net> <20160516231056.GE18496@dastard> <20160517144912.GZ3193@twins.programming.kicks-ass.net> <20160517223549.GV26977@dastard> <20160519081146.GS3193@twins.programming.kicks-ass.net> <20160520001714.GC26977@dastard> <20160601131758.GO26601@dhcp22.suse.cz> <20160601181617.GV3190@twins.programming.kicks-ass.net> <20161006130454.GI10570@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161006130454.GI10570@dhcp22.suse.cz> List-ID: To: Michal Hocko Cc: Peter Zijlstra , "Darrick J. Wong" , Qu Wenruo , xfs@oss.sgi.com, linux-mm@kvack.org, Ingo Molnar 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