[PATCH] um: Call pgtable_pmd_page_dtor() in __pmd_free_tlb()

[Christopher Obbard]

On Mon, Oct 19, 2020 at 11:10:49PM +0200, Richard Weinberger wrote:
> Commit b2b29d6d0119 ("mm: account PMD tables like PTE tables") uncovered
> a bug in uml, we forgot to call the destructor.
> While we are here, give x a sane name.
> 
> Reported-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
> Co-developed-by: Matthew Wilcox <willy at infradead.org>
> Signed-off-by: Richard Weinberger <richard at nod.at>

Tested-by: Christopher Obbard <chris.obbard at collabora.com>