Convert bit_spin_lock to new locking bitops. Slub can use the non-atomic store
version to clear (I think?)

Signed-off-by: Nick Piggin <npiggin@suse.de>

---
 include/linux/bit_spinlock.h |   26 ++++++++++++++++++++++----
 mm/slub.c                    |    2 +-
 2 files changed, 23 insertions(+), 5 deletions(-)

Index: linux-2.6/include/linux/bit_spinlock.h
===================================================================
--- linux-2.6.orig/include/linux/bit_spinlock.h
+++ linux-2.6/include/linux/bit_spinlock.h
@@ -18,7 +18,7 @@ static inline void bit_spin_lock(int bit
 	 */
 	preempt_disable();
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-	while (test_and_set_bit(bitnum, addr)) {
+	while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
 		while (test_bit(bitnum, addr)) {
 			preempt_enable();
 			cpu_relax();
@@ -36,7 +36,7 @@ static inline int bit_spin_trylock(int b
 {
 	preempt_disable();
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-	if (test_and_set_bit(bitnum, addr)) {
+	if (unlikely(test_and_set_bit_lock(bitnum, addr))) {
 		preempt_enable();
 		return 0;
 	}
@@ -50,10 +50,28 @@ static inline int bit_spin_trylock(int b
  */
 static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
 {
+#ifdef CONFIG_DEBUG_SPINLOCK
+	BUG_ON(!test_bit(bitnum, addr));
+#endif
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+	clear_bit_unlock(bitnum, addr);
+#endif
+	preempt_enable();
+	__release(bitlock);
+}
+
+/*
+ *  bit-based spin_unlock()
+ *  non-atomic version, which can be used eg. if the bit lock itself is
+ *  protecting the rest of the flags in the word.
+ */
+static inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
+{
+#ifdef CONFIG_DEBUG_SPINLOCK
 	BUG_ON(!test_bit(bitnum, addr));
-	smp_mb__before_clear_bit();
-	clear_bit(bitnum, addr);
+#endif
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+	__clear_bit_unlock(bitnum, addr);
 #endif
 	preempt_enable();
 	__release(bitlock);
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c
+++ linux-2.6/mm/slub.c
@@ -1124,7 +1124,7 @@ static __always_inline void slab_lock(st
 
 static __always_inline void slab_unlock(struct page *page)
 {
-	bit_spin_unlock(PG_locked, &page->flags);
+	__bit_spin_unlock(PG_locked, &page->flags);
 }
 
 static __always_inline int slab_trylock(struct page *page)