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SubjectRe: [PATCH -alternative] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables V2 (resend)
On Thu, Jul 26, 2012 at 01:42:26PM -0400, Rik van Riel wrote:
> On 07/23/2012 12:04 AM, Hugh Dickins wrote:
>
> >Please don't be upset if I say that I don't like either of your patches.
> >Mainly for obvious reasons - I don't like Mel's because anything with
> >trylock retries and nested spinlocks worries me before I can even start
> >to think about it; and I don't like Michal's for the same reason as Mel,
> >that it spreads more change around in common paths than we would like.
>
> I have a naive question.
>
> In huge_pmd_share, we protect ourselves by taking
> the mapping->i_mmap_mutex.
>
> Is there any reason we could not take the i_mmap_mutex
> in the huge_pmd_unshare path?
>

We do, in 3.4 at least - callers of __unmap_hugepage_range hold the
i_mmap_mutex. Locking changes in mmotm and there is a patch there that
needs to be reverted. What tree are you looking at?

--
Mel Gorman
SUSE Labs


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