mm: move ptep_get() and pmdp_get() helpers

There are many call sites that directly dereference a pte_t pointer.  This
makes it very difficult to properly encapsulate a page table in the arch
code without having to allocate shadow page tables.

We will shortly solve this by replacing all the call sites with ptep_get()
calls.  But there are call sites above the function definition in the
header file, so let's move ptep_get() to an earlier location to solve that
problem.  And move pmdp_get() at the same time to keep it close to
ptep_get().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ryan Roberts <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alex Williamson <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Dimitri Sivanich <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport (IBM) <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Oleksandr Tyshchenko <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: SeongJae Park <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Uladzislau Rezki (Sony) <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Ryan Roberts

include/linux/pgtable.h

@@ -212,6 +212,20 @@ static inline int pudp_set_access_flags(struct vm_area_struct *vma,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
+#ifndef ptep_get
+static inline pte_t ptep_get(pte_t *ptep)
+{
+	return READ_ONCE(*ptep);
+}
+#endif
+
+#ifndef pmdp_get
+static inline pmd_t pmdp_get(pmd_t *pmdp)
+{
+	return READ_ONCE(*pmdp);
+}
+#endif
+
 #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
@@ -317,20 +331,6 @@ static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
 	ptep_get_and_clear(mm, addr, ptep);
 }
 
-#ifndef ptep_get
-static inline pte_t ptep_get(pte_t *ptep)
-{
-	return READ_ONCE(*ptep);
-}
-#endif
-
-#ifndef pmdp_get
-static inline pmd_t pmdp_get(pmd_t *pmdp)
-{
-	return READ_ONCE(*pmdp);
-}
-#endif
-
 #ifdef CONFIG_GUP_GET_PXX_LOW_HIGH
 /*
  * For walking the pagetables without holding any locks.  Some architectures