Messages in this thread | | | Date | Tue, 2 Feb 2010 17:44:09 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH -mm] remove VM_LOCK_RMAP code |
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On Mon, Feb 01, 2010 at 10:55:35AM -0500, Rik van Riel wrote: > On 02/01/2010 01:15 AM, Nick Piggin wrote: > >On Fri, Jan 29, 2010 at 07:34:10PM -0500, Rik van Riel wrote: > >>When a VMA is in an inconsistent state during setup or teardown, the > >>worst that can happen is that the rmap code will not be able to find > >>the page. > > > >OK, but you missed the interesting thing, which is to explain why > >that worst case is not a problem. > > > >rmap of course is not just used for reclaim but also invalidations > >from mappings, and those guys definitely need to know that all > >page table entries have been handled by the time they return. > > This is not a problem, because the mapping is in the process > of being torn down (PTEs just got invalidated by munmap), or > set up (no PTEs have been instantiated yet). > > The third case is split_vma, where we can have one VMA in an > inconsistent state (rmap cannot find the PTEs), while the > other VMA is still in its original state (rmap finds the PTEs > through that VMA). > > That is what makes this safe.
OK, that sounds fine then. Your changelog was just a bit strange because you said it would not be able to find the page, which didn't really make sense.
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