mm: re-allow pinning of zero pfns
The commit referenced below subtly and inadvertently changed the logic to disallow pinning of zero pfns. This breaks device assignment with vfio and potentially various other users of gup. Exclude the zero page test from the negation. Link: https://lkml.kernel.org/r/165490039431.944052.12458624139225785964.stgit@omen Fixes: 1c563432 ("mm: fix is_pinnable_page against a cma page") Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Reported-by: Yishai Hadas <yishaih@nvidia.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: John Dias <joaodias@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Zhangfei Gao <zhangfei.gao@linaro.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Joao Martins <joao.m.martins@oracle.com> Cc: Yi Liu <yi.l.liu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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