FROMGIT: mm/hugetlb: fix build with !ARCH_WANT_HUGE_PMD_SHARE

want_pmd_share() is undefined with !ARCH_WANT_HUGE_PMD_SHARE since it's
put by accident into a "#ifdef ARCH_WANT_HUGE_PMD_SHARE" block.  Moving it
out won't work either since vma_shareable() is only defined within the
block.  Define it for !ARCH_WANT_HUGE_PMD_SHARE instead.

Link: https://lkml.kernel.org/r/20210310185359.88297-1-peterx@redhat.com
Fixes: 5b109cc1cdcc ("hugetlb/userfaultfd: forbid huge pmd sharing when uffd enabled")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

(cherry picked from commit 5038f9dd8bbde13ff16435011bb3b0981acc5c1c
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Link: https://lore.kernel.org/patchwork/patch/1393174/

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Bug: 160737021
Bug: 169683130
Change-Id: Id716afd43bff303f7eda2c4f70f18d9ea727c698

mm/hugetlb.c

@@ -5333,9 +5333,6 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr)
 
 bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
 {
-#ifndef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
-	return false;
-#endif
 #ifdef CONFIG_USERFAULTFD
 	if (uffd_disable_huge_pmd_share(vma))
 		return false;
@@ -5480,6 +5477,11 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
 				unsigned long *start, unsigned long *end)
 {
 }
+
+bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
+{
+	return false;
+}
 #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
 
 #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB