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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
    > PA-RISC)
    > > 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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