thp: add HPAGE_PMD_* definitions for !CONFIG_TRANSPARENT_HUGEPAGE

These macros will be used in a later patch, where all usages are expected
to be optimized away without #ifdef CONFIG_TRANSPARENT_HUGEPAGE.  But to
detect unexpected usages, we convert the existing BUG() to BUILD_BUG().

[akpm@linux-foundation.org: fix build in mm/pgtable-generic.c]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 9 insertions, 7 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f56cacb4fec3..c8af7a2efb52 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -51,6 +51,9 @@ extern pmd_t *page_check_address_pmd(struct page *page,
                                      unsigned long address,
                                      enum page_check_address_pmd_flag flag);
 
+#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
+#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define HPAGE_PMD_SHIFT HPAGE_SHIFT
 #define HPAGE_PMD_MASK HPAGE_MASK
@@ -102,8 +105,6 @@ extern void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd);
                 BUG_ON(pmd_trans_splitting(*____pmd) ||                 \
                        pmd_trans_huge(*____pmd));                       \
         } while (0)
-#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
-#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
 #if HPAGE_PMD_ORDER > MAX_ORDER
 #error "hugepages can't be allocated by the buddy allocator"
 #endif
@@ -158,9 +159,9 @@ static inline struct page *compound_trans_head(struct page *page)
         return page;
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
-#define HPAGE_PMD_SHIFT ({ BUG(); 0; })
-#define HPAGE_PMD_MASK ({ BUG(); 0; })
-#define HPAGE_PMD_SIZE ({ BUG(); 0; })
+#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
+#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
+#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })
 
 #define hpage_nr_pages(x) 1
 
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index eb663fb533e0..5a74fea182f1 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -70,10 +70,11 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
                            unsigned long address, pmd_t *pmdp)
 {
         int young;
-#ifndef CONFIG_TRANSPARENT_HUGEPAGE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+#else
         BUG();
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
         young = pmdp_test_and_clear_young(vma, address, pmdp);
         if (young)
                 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);