Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges

Andrea Arcangeli
2008-01-30T00:06:23Z

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.