Re: [PATCH 18/19] x86, mpx: do not count MPX VMAs as neighbors when unmapping

[Thomas Gleixner]

On Fri, 8 May 2015, Dave Hansen wrote:
> The comment pretty much says it all.
> 
> I wrote a test program that does lots of random allocations
> and forces bounds tables to be created.  It came up with a
> layout like this:
> 
>   ....   | BOUNDS DIRECTORY ENTRY COVERS |  ....
>          |    BOUNDS TABLE COVERS        |
> |  BOUNDS TABLE |  REAL ALLOC | BOUNDS TABLE |
> 
> Unmapping "REAL ALLOC" should have been able to free the
> bounds table "covering" the "REAL ALLOC" because it was the
> last real user.  But, the neighboring VMA bounds tables were
> found, considered as real neighbors, and we declined to free
> the bounds table covering the area.
> 
> Doing this over and over left a small but significant number
> of these orphans.  Handling them is fairly straighforward.
> All we have to do is walk the VMAs and skip all of the MPX
> ones when looking for neighbors.
> 
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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