mm: slub: SLUB_DEBUG=n: use the same alloc/free hooks as for SLUB_DEBUG=y

There are two versions of alloc/free hooks now - one for
CONFIG_SLUB_DEBUG=y and another one for CONFIG_SLUB_DEBUG=n.

I see no reason why calls to other debugging subsystems (LOCKDEP,
DEBUG_ATOMIC_SLEEP, KMEMCHECK and FAILSLAB) are hidden under SLUB_DEBUG.
All this features should work regardless of SLUB_DEBUG config, as all of
them already have own Kconfig options.

This also fixes failslab for CONFIG_SLUB_DEBUG=n configuration.  It
simply has not worked before because should_failslab() call was in a
hook hidden under "#ifdef CONFIG_SLUB_DEBUG #else".

Note: There is one concealed change in allocation path for SLUB_DEBUG=n
and all other debugging features disabled.  The might_sleep_if() call
can generate some code even if DEBUG_ATOMIC_SLEEP=n.  For
PREEMPT_VOLUNTARY=y might_sleep() inserts _cond_resched() call, but I
think it should be ok.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -939,60 +939,6 @@ static void trace(struct kmem_cache *s, struct page *page, void *object,
 	}
 }
 
-/*
- * Hooks for other subsystems that check memory allocations. In a typical
- * production configuration these hooks all should produce no code at all.
- */
-static inline void kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
-{
-	kmemleak_alloc(ptr, size, 1, flags);
-}
-
-static inline void kfree_hook(const void *x)
-{
-	kmemleak_free(x);
-}
-
-static inline int slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
-{
-	flags &= gfp_allowed_mask;
-	lockdep_trace_alloc(flags);
-	might_sleep_if(flags & __GFP_WAIT);
-
-	return should_failslab(s->object_size, flags, s->flags);
-}
-
-static inline void slab_post_alloc_hook(struct kmem_cache *s,
-					gfp_t flags, void *object)
-{
-	flags &= gfp_allowed_mask;
-	kmemcheck_slab_alloc(s, flags, object, slab_ksize(s));
-	kmemleak_alloc_recursive(object, s->object_size, 1, s->flags, flags);
-}
-
-static inline void slab_free_hook(struct kmem_cache *s, void *x)
-{
-	kmemleak_free_recursive(x, s->flags);
-
-	/*
-	 * Trouble is that we may no longer disable interrupts in the fast path
-	 * So in order to make the debug calls that expect irqs to be
-	 * disabled we need to disable interrupts temporarily.
-	 */
-#if defined(CONFIG_KMEMCHECK) || defined(CONFIG_LOCKDEP)
-	{
-		unsigned long flags;
-
-		local_irq_save(flags);
-		kmemcheck_slab_free(s, x, s->object_size);
-		debug_check_no_locks_freed(x, s->object_size);
-		local_irq_restore(flags);
-	}
-#endif
-	if (!(s->flags & SLAB_DEBUG_OBJECTS))
-		debug_check_no_obj_freed(x, s->object_size);
-}
-
 /*
  * Tracking of fully allocated slabs for debugging purposes.
  */
@@ -1277,6 +1223,12 @@ static inline void inc_slabs_node(struct kmem_cache *s, int node,
 static inline void dec_slabs_node(struct kmem_cache *s, int node,
 							int objects) {}
 
+#endif /* CONFIG_SLUB_DEBUG */
+
+/*
+ * Hooks for other subsystems that check memory allocations. In a typical
+ * production configuration these hooks all should produce no code at all.
+ */
 static inline void kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
 {
 	kmemleak_alloc(ptr, size, 1, flags);
@@ -1288,21 +1240,44 @@ static inline void kfree_hook(const void *x)
 }
 
 static inline int slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
-							{ return 0; }
+{
+	flags &= gfp_allowed_mask;
+	lockdep_trace_alloc(flags);
+	might_sleep_if(flags & __GFP_WAIT);
 
-static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
-		void *object)
+	return should_failslab(s->object_size, flags, s->flags);
+}
+
+static inline void slab_post_alloc_hook(struct kmem_cache *s,
+					gfp_t flags, void *object)
 {
-	kmemleak_alloc_recursive(object, s->object_size, 1, s->flags,
-		flags & gfp_allowed_mask);
+	flags &= gfp_allowed_mask;
+	kmemcheck_slab_alloc(s, flags, object, slab_ksize(s));
+	kmemleak_alloc_recursive(object, s->object_size, 1, s->flags, flags);
 }
 
 static inline void slab_free_hook(struct kmem_cache *s, void *x)
 {
 	kmemleak_free_recursive(x, s->flags);
-}
 
-#endif /* CONFIG_SLUB_DEBUG */
+	/*
+	 * Trouble is that we may no longer disable interrupts in the fast path
+	 * So in order to make the debug calls that expect irqs to be
+	 * disabled we need to disable interrupts temporarily.
+	 */
+#if defined(CONFIG_KMEMCHECK) || defined(CONFIG_LOCKDEP)
+	{
+		unsigned long flags;
+
+		local_irq_save(flags);
+		kmemcheck_slab_free(s, x, s->object_size);
+		debug_check_no_locks_freed(x, s->object_size);
+		local_irq_restore(flags);
+	}
+#endif
+	if (!(s->flags & SLAB_DEBUG_OBJECTS))
+		debug_check_no_obj_freed(x, s->object_size);
+}
 
 /*
  * Slab allocation and freeing