[PATCH RFC 02/12] mm: Provide generic pmd_thp_or_huge()

[Peter Xu <peterx@redhat.com>]

ARM defines pmd_thp_or_huge(), detecting either a THP or a huge PMD.  It
can be a helpful helper if we want to merge more THP and hugetlb code
paths.  Make it a generic default implementation, only exist when
CONFIG_MMU.  Arch can overwrite it by defining its own version.

For example, ARM's pgtable-2level.h defines it to always return false.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/linux/pgtable.h | 4 ++++
 mm/gup.c                | 3 +--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index af7639c3b0a3..6f2fa1977b8a 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1355,6 +1355,10 @@ static inline int pmd_write(pmd_t pmd)
 #endif /* pmd_write */
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+#ifndef pmd_thp_or_huge
+#define pmd_thp_or_huge(pmd)	(pmd_huge(pmd) || pmd_trans_huge(pmd))
+#endif
+
 #ifndef pud_write
 static inline int pud_write(pud_t pud)
 {
diff --git a/mm/gup.c b/mm/gup.c
index 231711efa390..a8b73a8289ad 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3002,8 +3002,7 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo
 		if (!pmd_present(pmd))
 			return 0;
 
-		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
-			     pmd_devmap(pmd))) {
+		if (unlikely(pmd_thp_or_huge(pmd) || pmd_devmap(pmd))) {
 			/* See gup_pte_range() */
 			if (pmd_protnone(pmd))
 				return 0;
-- 
2.41.0