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    SubjectRe: [PATCH 1/6] freepgt: free_pgtables use vma list
    On Tue, Mar 29, 2005 at 11:03:02PM +0100, Hugh Dickins wrote:
    > > Nice approach....
    > Thanks.
    > > It will not work as well
    > > on large sparse mappings as the bit vectors, but that may be tolerable.
    > Exactly. It's simply what what we should be doing first, making use of
    > the infrastructure we already have. If that proves inadequate, add on top.

    Ok. I will defer the bitvector patch now.

    I had it mostly working with hacks, but than I ran into
    a nasty include ordering problem that scared me off so far.

    > I do. I'll resend you an earlier mail I wrote about it, I think x86_64
    > is liable to leak pagetables or conversely rip pagetables out from under
    > the vsyscall page - in the 32-bit emulation case, with my patches, if
    > that vsyscall page has been mapped. That it'll be fine or unnoticed
    > most of the time, but really not right.
    > I'll also resend you Ben's mail on the subject, what he does on ppc64.

    > Ah, you do SetPageReserved on that page. That's good, rmap would have
    > a problem with it, since it doesn't belong to a file, yet is shared
    > between all tasks, so is quite unlike an anonymous page. I suggest
    > you make the vma VM_RESERVED too, but that doesn't really matter yet.

    Ok. I will change it to a VMA.

    Only bad thing is that this has to be done at program startup.
    At fault time we cannot upgrade the read lock on mmap sem to a write
    lock that is needed to insert the VMA :/ But I guess that is ok
    because with modern glibc basically all programs will use vsyscsall.

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      Last update: 2005-04-06 13:31    [W:0.026 / U:109.512 seconds]
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