Re: [PATCH] Initialise mmu_notifier_range correctly

From: Matthew Wilcox
Date: Thu Jan 03 2019 - 09:36:51 EST

On Thu, Jan 03, 2019 at 09:31:16AM -0500, Jerome Glisse wrote:
> On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
> >
> > One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> > incorrectly.
> >
> > Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for invalidate_range_start/end calls v2")
> > Tested-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Actually now that i have read the code again this is not ok to
> do so. The caller of follow_pte_pmd() will call range_init and
> follow pmd will only update the range address. So existing code
> is ok.

The only caller of follow_pte_pmd() does not call range_init() because it
doesn't know the address. That's the point of follow_pte_pmd().

> I know this is kind of ugly but i do not see a way around that
> uglyness.

You wrote the code ...