commit bd5e88ad72b26ebf7ecb231bc22ceecd6cbdb951
author Vineet Gupta <vgupta@synopsys.com> Thu Jul 09 17:22:44 2015 +0530
committer Vineet Gupta <vgupta@synopsys.com> Sat Oct 17 17:48:20 2015 +0530
tree cb9da0478c769d706cec2e9fbd140172e05b5366
parent 52585bcc2505d6f888d4ac68ca6c55f6d1ad736a

mm,thp: reduce ifdef'ery for THP in generic code

- pgtable-generic.c: Fold individual #ifdef for each helper into a top
  level #ifdef. Makes code more readable

- Converted the stub helpers for !THP to BUILD_BUG() vs. runtime BUG()

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20151009133450.GA8597@node
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

include/asm-generic/pgtable.h

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 29c57b2..3eabbbb 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -30,9 +30,19 @@
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern int pmdp_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp,
 				 pmd_t entry, int dirty);
+#else
+static inline int pmdp_set_access_flags(struct vm_area_struct *vma,
+					unsigned long address, pmd_t *pmdp,
+					pmd_t entry, int dirty)
+{
+	BUILD_BUG();
+	return 0;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
 #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
@@ -64,12 +74,12 @@
 		set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
 	return r;
 }
-#else /* CONFIG_TRANSPARENT_HUGEPAGE */
+#else
 static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
 					    pmd_t *pmdp)
 {
-	BUG();
+	BUILD_BUG();
 	return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -81,8 +91,21 @@
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
-int pmdp_clear_flush_young(struct vm_area_struct *vma,
-			   unsigned long address, pmd_t *pmdp);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
+				  unsigned long address, pmd_t *pmdp);
+#else
+/*
+ * Despite relevant to THP only, this API is called from generic rmap code
+ * under PageTransHuge(), hence needs a dummy implementation for !THP
+ */
+static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
+					 unsigned long address, pmd_t *pmdp)
+{
+	BUILD_BUG();
+	return 0;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
@@ -175,11 +198,11 @@
 	pmd_t old_pmd = *pmdp;
 	set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
 }
-#else /* CONFIG_TRANSPARENT_HUGEPAGE */
+#else
 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 				      unsigned long address, pmd_t *pmdp)
 {
-	BUG();
+	BUILD_BUG();
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
@@ -248,7 +271,7 @@
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 {
-	BUG();
+	BUILD_BUG();
 	return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */