On Sun, 2015-12-20 at 10:27 +0100, Thomas Gleixner wrote:
> Toshi,
>
> On Wed, 9 Dec 2015, Toshi Kani wrote:
> > diff --git a/arch/x86/mm/pat_rbtree.c b/arch/x86/mm/pat_rbtree.c
> > index 6393108..d6faef8 100644
> > --- a/arch/x86/mm/pat_rbtree.c
> > +++ b/arch/x86/mm/pat_rbtree.c
> > @@ -107,7 +112,12 @@ static struct memtype
> > *memtype_rb_exact_match(struct rb_root *root,
> > while (match != NULL && match->start < end) {
> > struct rb_node *node;
> >
> > - if (match->start == start && match->end == end)
> > + if ((match_type == MEMTYPE_EXACT_MATCH) &&
> > + (match->start == start) && (match->end == end))
> > + return match;
> > +
> > + if ((match_type == MEMTYPE_SHRINK_MATCH) &&
> > + (match->start < start) && (match->end == end))
>
> Confused. If we shrink a mapping then I'd expect that the start of the
> mapping stays the same and the end changes.
Yes, that is correct after this request is done.
> I certainly miss something here, but if the above is correct, then it
> definitely needs a big fat comment explaining it.
This request specifies a range being "unmapped", not the remaining mapped
range. So, when the mapping range is going to shrink from the end, the
unmapping range has a bigger 'start' value and the same 'end' value.
Thanks,
-Toshi
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