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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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