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SubjectRe: [2/3] mm: fix up some user-visible effects of the stack guard page
On Fri, 2010-08-20 at 17:32 +0100, Ian Campbell wrote:

> On Fri, 2010-08-20 at 09:07 -0700, Linus Torvalds wrote:
> > Actually, thinking some more about it, that may not be a good idea.
> > Why? Simply because we may want to merge the vma's back together if
> > you do munlock. And it won't (and mustn't) merge if the vm_flags
> > differ in VM_GROWSDOWN.
> >
> > So I do think we want to keep VM_GROWSDOWN (and VM_GROWSUP on
> > even across a vma split.
> I naively hacked something together and it did seem to work, but I
> shared your worries about merging.
> > Of course, we could set a flag whether the vma really does have a
> > guard page or not.
> Bits in vma->vm_flags seems to be in rather short supply :-(

On the other hand the VMA merging is just an optimisation, isn't it?

Ian Campbell

Many people are desperately looking for some wise advice which will
recommend that they do what they want to do.

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