Re: [PATCH] hugetlb: fix lockdep splat caused by pmd sharing

[Dave Jones]

On Wed, Jul 31, 2013 at 08:35:30AM +0900, Minchan Kim wrote:
 > > which is a false positive caused by hugetlb pmd sharing code which
 > > allocates a new pmd from withing mappint->i_mmap_mutex. If this
 > > allocation causes reclaim then the lockdep detector complains that we
 > > might self-deadlock.
 > > 
 > > This is not correct though, because hugetlb pages are not reclaimable so
 > > their mapping will be never touched from the reclaim path.
 > > 
 > > The patch tells lockup detector that hugetlb i_mmap_mutex is special
 > > by assigning it a separate lockdep class so it won't report possible
 > > deadlocks on unrelated mappings.
 > > 
 > > [peterz@xxxxxxxxxxxxx: comment for annotation]
 > > Reported-by: Dave Jones <davej@xxxxxxxxxx>
 > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
 > Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx>
 > 
 > Thanks, Michal!
 > Only remained thing is Dave's testing.

I've added it to my builds, all is quiet so far..

	Dave





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