Re: [RFC] hugetlb reservations -- MAP_PRIVATE fixes for split vmas V2

[Jon Tollefson <kniht@linux.vnet.ibm.com>]

Andy Whitcroft wrote:
> As reported by Adam Litke and Jon Tollefson one of the libhugetlbfs
> regression tests triggers a negative overall reservation count.  When
> this occurs where there is no dynamic pool enabled tests will fail.
>
> Following this email are two patches to address this issue:
>
> hugetlb reservations: move region tracking earlier -- simply moves the
>   region tracking code earlier so we do not have to supply prototypes, and
>
> hugetlb reservations: fix hugetlb MAP_PRIVATE reservations across vma
>   splits -- which moves us to tracking the consumed reservation so that
>   we can correctly calculate the remaining reservations at vma close time.
>
> This stack is against the top of v2.6.25-rc6-mm3, should this solution
> prove acceptable it would need slipping underneath Nick's multiple hugepage
> size patches and those updated.  I have a modified stack prepared for that.
>
> This version incorporates Mel's feedback (both cosmetic, and an allocation
> under spinlock issue) and has an improved layout.
>
> Changes in V2:
>  - commentry updates
>  - pull allocations out from under hugetlb_lock
>  - refactor to match shared code layout
>  - reinstate BUG_ON's
>
> Jon could you have a test on this and see if it works out for you.
>
> -apw
>   
Version two works for me too.  I am not seeing the reserve value become
negative when running the libhuge tests.

Jon

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