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Date: Tue, 2 Feb 2010 17:44:09 +1100 From: Nick Piggin <npiggin@...e.de> To: Rik van Riel <riel@...hat.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, lwoodman@...hat.com, Lee Schermerhorn <Lee.Schermerhorn@...com>, aarcange@...hat.com Subject: Re: [PATCH -mm] remove VM_LOCK_RMAP code 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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