[RFC PATCH] mm/slub: remove left-over debugging code

[Qian Cai <cai@lca.pw>]

SLUB_RESILIENCY_TEST and SLUB_DEBUG_CMPXCHG look like some left-over
debugging code during the internal development that probably nobody uses
it anymore. Remove them to make the world greener.
---
 mm/slub.c | 110 --------------------------------------------------------------
 1 file changed, 110 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8834563cdb4b..f97155ba097d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -150,12 +150,6 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
  * - Variable sizing of the per node arrays
  */
 
-/* Enable to test recovery from slab corruption on boot */
-#undef SLUB_RESILIENCY_TEST
-
-/* Enable to log cmpxchg failures */
-#undef SLUB_DEBUG_CMPXCHG
-
 /*
  * Mininum number of partial slabs. These will be left on the partial
  * lists even if they are empty. kmem_cache_shrink may reclaim them.
@@ -392,10 +386,6 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page
 	cpu_relax();
 	stat(s, CMPXCHG_DOUBLE_FAIL);
 
-#ifdef SLUB_DEBUG_CMPXCHG
-	pr_info("%s %s: cmpxchg double redo ", n, s->name);
-#endif
-
 	return false;
 }
 
@@ -433,10 +423,6 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 	cpu_relax();
 	stat(s, CMPXCHG_DOUBLE_FAIL);
 
-#ifdef SLUB_DEBUG_CMPXCHG
-	pr_info("%s %s: cmpxchg double redo ", n, s->name);
-#endif
-
 	return false;
 }
 
@@ -2004,45 +1990,11 @@ static inline unsigned long next_tid(unsigned long tid)
 	return tid + TID_STEP;
 }
 
-static inline unsigned int tid_to_cpu(unsigned long tid)
-{
-	return tid % TID_STEP;
-}
-
-static inline unsigned long tid_to_event(unsigned long tid)
-{
-	return tid / TID_STEP;
-}
-
 static inline unsigned int init_tid(int cpu)
 {
 	return cpu;
 }
 
-static inline void note_cmpxchg_failure(const char *n,
-		const struct kmem_cache *s, unsigned long tid)
-{
-#ifdef SLUB_DEBUG_CMPXCHG
-	unsigned long actual_tid = __this_cpu_read(s->cpu_slab->tid);
-
-	pr_info("%s %s: cmpxchg redo ", n, s->name);
-
-#ifdef CONFIG_PREEMPT
-	if (tid_to_cpu(tid) != tid_to_cpu(actual_tid))
-		pr_warn("due to cpu change %d -> %d\n",
-			tid_to_cpu(tid), tid_to_cpu(actual_tid));
-	else
-#endif
-	if (tid_to_event(tid) != tid_to_event(actual_tid))
-		pr_warn("due to cpu running other code. Event %ld->%ld\n",
-			tid_to_event(tid), tid_to_event(actual_tid));
-	else
-		pr_warn("for unknown reason: actual=%lx was=%lx target=%lx\n",
-			actual_tid, tid, next_tid(tid));
-#endif
-	stat(s, CMPXCHG_DOUBLE_CPU_FAIL);
-}
-
 static void init_kmem_cache_cpus(struct kmem_cache *s)
 {
 	int cpu;
@@ -2751,7 +2703,6 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
 				object, tid,
 				next_object, next_tid(tid)))) {
 
-			note_cmpxchg_failure("slab_alloc", s, tid);
 			goto redo;
 		}
 		prefetch_freepointer(s, next_object);
@@ -4694,66 +4645,6 @@ static int list_locations(struct kmem_cache *s, char *buf,
 }
 #endif	/* CONFIG_SLUB_DEBUG */
 
-#ifdef SLUB_RESILIENCY_TEST
-static void __init resiliency_test(void)
-{
-	u8 *p;
-	int type = KMALLOC_NORMAL;
-
-	BUILD_BUG_ON(KMALLOC_MIN_SIZE > 16 || KMALLOC_SHIFT_HIGH < 10);
-
-	pr_err("SLUB resiliency testing\n");
-	pr_err("-----------------------\n");
-	pr_err("A. Corruption after allocation\n");
-
-	p = kzalloc(16, GFP_KERNEL);
-	p[16] = 0x12;
-	pr_err("\n1. kmalloc-16: Clobber Redzone/next pointer 0x12->0x%p\n\n",
-	       p + 16);
-
-	validate_slab_cache(kmalloc_caches[type][4]);
-
-	/* Hmmm... The next two are dangerous */
-	p = kzalloc(32, GFP_KERNEL);
-	p[32 + sizeof(void *)] = 0x34;
-	pr_err("\n2. kmalloc-32: Clobber next pointer/next slab 0x34 -> -0x%p\n",
-	       p);
-	pr_err("If allocated object is overwritten then not detectable\n\n");
-
-	validate_slab_cache(kmalloc_caches[type][5]);
-	p = kzalloc(64, GFP_KERNEL);
-	p += 64 + (get_cycles() & 0xff) * sizeof(void *);
-	*p = 0x56;
-	pr_err("\n3. kmalloc-64: corrupting random byte 0x56->0x%p\n",
-	       p);
-	pr_err("If allocated object is overwritten then not detectable\n\n");
-	validate_slab_cache(kmalloc_caches[type][6]);
-
-	pr_err("\nB. Corruption after free\n");
-	p = kzalloc(128, GFP_KERNEL);
-	kfree(p);
-	*p = 0x78;
-	pr_err("1. kmalloc-128: Clobber first word 0x78->0x%p\n\n", p);
-	validate_slab_cache(kmalloc_caches[type][7]);
-
-	p = kzalloc(256, GFP_KERNEL);
-	kfree(p);
-	p[50] = 0x9a;
-	pr_err("\n2. kmalloc-256: Clobber 50th byte 0x9a->0x%p\n\n", p);
-	validate_slab_cache(kmalloc_caches[type][8]);
-
-	p = kzalloc(512, GFP_KERNEL);
-	kfree(p);
-	p[512] = 0xab;
-	pr_err("\n3. kmalloc-512: Clobber redzone 0xab->0x%p\n\n", p);
-	validate_slab_cache(kmalloc_caches[type][9]);
-}
-#else
-#ifdef CONFIG_SYSFS
-static void resiliency_test(void) {};
-#endif
-#endif	/* SLUB_RESILIENCY_TEST */
-
 #ifdef CONFIG_SYSFS
 enum slab_stat_type {
 	SL_ALL,			/* All slabs */
@@ -5875,7 +5766,6 @@ static int __init slab_sysfs_init(void)
 	}
 
 	mutex_unlock(&slab_mutex);
-	resiliency_test();
 	return 0;
 }
 
-- 
1.8.3.1