Re: [PATCH] mm, numa: Fix bad pmd by atomically check for pmd_trans_huge when marking page tables prot_numa

[Mel Gorman]

On Mon, Apr 10, 2017 at 11:45:08AM -0500, Zi Yan wrote:
> > While this could be fixed with heavy locking, it's only necessary to
> > make a copy of the PMD on the stack during change_pmd_range and avoid
> > races. A new helper is created for this as the check if quite subtle and the
> > existing similar helpful is not suitable. This passed 154 hours of testing
> > (usually triggers between 20 minutes and 24 hours) without detecting bad
> > PMDs or corruption. A basic test of an autonuma-intensive workload showed
> > no significant change in behaviour.
> >
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> 
> Does this patch fix the same problem fixed by Kirill's patch here?
> https://lkml.org/lkml/2017/3/2/347
> 

I don't think so. The race I'm concerned with is due to locks not being
held and is in a different path.

-- 
Mel Gorman
SUSE Labs