mm: properly separate the bloated ptl from the regular case

Use kernel/bounds.c to convert build-time spinlock_t size check into a
preprocessor symbol and apply that to properly separate the page::ptl
situation.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 11 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d0339741b6ce..1cedd000cf29 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1317,27 +1317,29 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a
 #endif /* CONFIG_MMU && !__ARCH_HAS_4LEVEL_HACK */
 
 #if USE_SPLIT_PTE_PTLOCKS
-bool __ptlock_alloc(struct page *page);
-void __ptlock_free(struct page *page);
+#if BLOATED_SPINLOCKS
+extern bool ptlock_alloc(struct page *page);
+extern void ptlock_free(struct page *page);
+
+static inline spinlock_t *ptlock_ptr(struct page *page)
+{
+	return page->ptl;
+}
+#else /* BLOATED_SPINLOCKS */
 static inline bool ptlock_alloc(struct page *page)
 {
-	if (sizeof(spinlock_t) > sizeof(page->ptl))
-		return __ptlock_alloc(page);
 	return true;
 }
+
 static inline void ptlock_free(struct page *page)
 {
-	if (sizeof(spinlock_t) > sizeof(page->ptl))
-		__ptlock_free(page);
 }
 
 static inline spinlock_t *ptlock_ptr(struct page *page)
 {
-	if (sizeof(spinlock_t) > sizeof(page->ptl))
-		return (spinlock_t *) page->ptl;
-	else
-		return (spinlock_t *) &page->ptl;
+	return &page->ptl;
 }
+#endif /* BLOATED_SPINLOCKS */
 
 static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
 {
@@ -1354,7 +1356,7 @@ static inline bool ptlock_init(struct page *page)
 	 * slab code uses page->slab_cache and page->first_page (for tail
 	 * pages), which share storage with page->ptl.
 	 */
-	VM_BUG_ON(page->ptl);
+	VM_BUG_ON(*(unsigned long *)&page->ptl);
 	if (!ptlock_alloc(page))
 		return false;
 	spin_lock_init(ptlock_ptr(page));