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    SubjectRe: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges
    On Wed, 30 Jan 2008, Andrea Arcangeli wrote:

    > On Wed, Jan 30, 2008 at 01:00:39AM +0100, Andrea Arcangeli wrote:
    > > get_user_pages, regular linux writes don't fault unless it's
    > > explicitly writeprotect, which is mandatory in a few archs, x86 not).
    > actually get_user_pages doesn't fault either but it calls into
    > set_page_dirty, however get_user_pages (unlike a userland-write) at
    > least requires mmap_sem in read mode and the PT lock as serialization,
    > userland writes don't, they just go ahead and mark the pte in hardware
    > w/o faults. Anyway anonymous memory these days always mapped with
    > dirty bit set regardless, even for read-faults, after Nick finally
    > rightfully cleaned up the zero-page trick.

    That is only partially true. pte are created wronly in order to track
    dirty state these days. The first write will lead to a fault that switches
    the pte to writable. When the page undergoes writeback the page again
    becomes write protected. Thus our need to effectively deal with

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      Last update: 2008-01-30 01:25    [W:0.019 / U:3.220 seconds]
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