diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
index f950c9d29f3e..2638417b19aa 100644
--- a/drivers/md/bcache/Kconfig
+++ b/drivers/md/bcache/Kconfig
@@ -13,15 +13,8 @@ config BCACHE_DEBUG
 	---help---
 	Don't select this option unless you're a developer
 
-	Enables extra debugging tools (primarily a fuzz tester)
-
-config BCACHE_EDEBUG
-	bool "Extended runtime checks"
-	depends on BCACHE
-	---help---
-	Don't select this option unless you're a developer
-
-	Enables extra runtime checks which significantly affect performance
+	Enables extra debugging tools, allows expensive runtime checks to be
+	turned on.
 
 config BCACHE_CLOSURES_DEBUG
 	bool "Debug closures"
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 4970ddc6a7f6..ed5920b20c61 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -398,8 +398,7 @@ long bch_bucket_alloc(struct cache *ca, unsigned watermark, bool wait)
 out:
 	wake_up_process(ca->alloc_thread);
 
-#ifdef CONFIG_BCACHE_EDEBUG
-	{
+	if (expensive_debug_checks(ca->set)) {
 		size_t iter;
 		long i;
 
@@ -413,7 +412,7 @@ out:
 		fifo_for_each(i, &ca->unused, iter)
 			BUG_ON(i == r);
 	}
-#endif
+
 	b = ca->buckets + r;
 
 	BUG_ON(atomic_read(&b->pin) != 1);
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 045cb99f1ca6..d03bc6f66493 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -690,6 +690,7 @@ struct cache_set {
 	unsigned short		journal_delay_ms;
 	unsigned		verify:1;
 	unsigned		key_merging_disabled:1;
+	unsigned		expensive_debug_checks:1;
 	unsigned		gc_always_rewrite:1;
 	unsigned		shrinker_disabled:1;
 	unsigned		copy_gc_enabled:1;
@@ -698,15 +699,6 @@ struct cache_set {
 	struct hlist_head	bucket_hash[1 << BUCKET_HASH_BITS];
 };
 
-static inline bool key_merging_disabled(struct cache_set *c)
-{
-#ifdef CONFIG_BCACHE_DEBUG
-	return c->key_merging_disabled;
-#else
-	return 0;
-#endif
-}
-
 struct bbio {
 	unsigned		submit_time_us;
 	union {
diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index f32216c75948..6bffde478926 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -106,6 +106,43 @@ bad:
 	return true;
 }
 
+static bool ptr_bad_expensive_checks(struct btree *b, const struct bkey *k,
+				     unsigned ptr)
+{
+	struct bucket *g = PTR_BUCKET(b->c, k, ptr);
+	char buf[80];
+
+	if (mutex_trylock(&b->c->bucket_lock)) {
+		if (b->level) {
+			if (KEY_DIRTY(k) ||
+			    g->prio != BTREE_PRIO ||
+			    (b->c->gc_mark_valid &&
+			     GC_MARK(g) != GC_MARK_METADATA))
+				goto err;
+
+		} else {
+			if (g->prio == BTREE_PRIO)
+				goto err;
+
+			if (KEY_DIRTY(k) &&
+			    b->c->gc_mark_valid &&
+			    GC_MARK(g) != GC_MARK_DIRTY)
+				goto err;
+		}
+		mutex_unlock(&b->c->bucket_lock);
+	}
+
+	return false;
+err:
+	mutex_unlock(&b->c->bucket_lock);
+	bch_bkey_to_text(buf, sizeof(buf), k);
+	btree_bug(b,
+"inconsistent pointer %s: bucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
+		  buf, PTR_BUCKET_NR(b->c, k, ptr), atomic_read(&g->pin),
+		  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
+	return true;
+}
+
 bool bch_ptr_bad(struct btree *b, const struct bkey *k)
 {
 	struct bucket *g;
@@ -133,46 +170,12 @@ bool bch_ptr_bad(struct btree *b, const struct bkey *k)
 		if (stale)
 			return true;
 
-#ifdef CONFIG_BCACHE_EDEBUG
-		if (!mutex_trylock(&b->c->bucket_lock))
-			continue;
-
-		if (b->level) {
-			if (KEY_DIRTY(k) ||
-			    g->prio != BTREE_PRIO ||
-			    (b->c->gc_mark_valid &&
-			     GC_MARK(g) != GC_MARK_METADATA))
-				goto bug;
-
-		} else {
-			if (g->prio == BTREE_PRIO)
-				goto bug;
-
-			if (KEY_DIRTY(k) &&
-			    b->c->gc_mark_valid &&
-			    GC_MARK(g) != GC_MARK_DIRTY)
-				goto bug;
-		}
-		mutex_unlock(&b->c->bucket_lock);
-#endif
+		if (expensive_debug_checks(b->c) &&
+		    ptr_bad_expensive_checks(b, k, i))
+			return true;
 	}
 
 	return false;
-#ifdef CONFIG_BCACHE_EDEBUG
-bug:
-	mutex_unlock(&b->c->bucket_lock);
-
-	{
-		char buf[80];
-
-		bch_bkey_to_text(buf, sizeof(buf), k);
-		btree_bug(b,
-"inconsistent pointer %s: bucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
-			  buf, PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
-			  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
-	}
-	return true;
-#endif
 }
 
 /* Key/pointer manipulation */
@@ -821,16 +824,16 @@ struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
 	} else
 		i = bset_search_write_set(b, t, search);
 
-#ifdef CONFIG_BCACHE_EDEBUG
-	BUG_ON(bset_written(b, t) &&
-	       i.l != t->data->start &&
-	       bkey_cmp(tree_to_prev_bkey(t,
-		  inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
-			search) > 0);
+	if (expensive_debug_checks(b->c)) {
+		BUG_ON(bset_written(b, t) &&
+		       i.l != t->data->start &&
+		       bkey_cmp(tree_to_prev_bkey(t,
+			  inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
+				search) > 0);
 
-	BUG_ON(i.r != end(t->data) &&
-	       bkey_cmp(i.r, search) <= 0);
-#endif
+		BUG_ON(i.r != end(t->data) &&
+		       bkey_cmp(i.r, search) <= 0);
+	}
 
 	while (likely(i.l != i.r) &&
 	       bkey_cmp(i.l, search) <= 0)
@@ -871,12 +874,16 @@ void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
 }
 
 struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
-			       struct bkey *search, struct bset_tree *start)
+				   struct bkey *search, struct bset_tree *start)
 {
 	struct bkey *ret = NULL;
 	iter->size = ARRAY_SIZE(iter->data);
 	iter->used = 0;
 
+#ifdef CONFIG_BCACHE_DEBUG
+	iter->b = b;
+#endif
+
 	for (; start <= &b->sets[b->nsets]; start++) {
 		ret = bch_bset_search(b, start, search);
 		bch_btree_iter_push(iter, ret, end(start->data));
@@ -891,6 +898,8 @@ struct bkey *bch_btree_iter_next(struct btree_iter *iter)
 	struct bkey *ret = NULL;
 
 	if (!btree_iter_end(iter)) {
+		bch_btree_iter_next_check(iter);
+
 		ret = iter->data->k;
 		iter->data->k = bkey_next(iter->data->k);
 
@@ -1002,7 +1011,6 @@ static void btree_mergesort(struct btree *b, struct bset *out,
 	out->keys = last ? (uint64_t *) bkey_next(last) - out->d : 0;
 
 	pr_debug("sorted %i keys", out->keys);
-	bch_check_key_order(b, out);
 }
 
 static void __btree_sort(struct btree *b, struct btree_iter *iter,
@@ -1063,15 +1071,15 @@ static void __btree_sort(struct btree *b, struct btree_iter *iter,
 
 void bch_btree_sort_partial(struct btree *b, unsigned start)
 {
-	size_t oldsize = 0, order = b->page_order, keys = 0;
+	size_t order = b->page_order, keys = 0;
 	struct btree_iter iter;
+	int oldsize = bch_count_data(b);
+
 	__bch_btree_iter_init(b, &iter, NULL, &b->sets[start]);
 
 	BUG_ON(b->sets[b->nsets].data == write_block(b) &&
 	       (b->sets[b->nsets].size || b->nsets));
 
-	if (b->written)
-		oldsize = bch_count_data(b);
 
 	if (start) {
 		unsigned i;
@@ -1087,7 +1095,7 @@ void bch_btree_sort_partial(struct btree *b, unsigned start)
 
 	__btree_sort(b, &iter, start, order, false);
 
-	EBUG_ON(b->written && bch_count_data(b) != oldsize);
+	EBUG_ON(b->written && oldsize >= 0 && bch_count_data(b) != oldsize);
 }
 
 void bch_btree_sort_and_fix_extents(struct btree *b, struct btree_iter *iter)
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index 5cd90565dfe2..a043a92d4dc9 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -148,6 +148,9 @@
 
 struct btree_iter {
 	size_t size, used;
+#ifdef CONFIG_BCACHE_DEBUG
+	struct btree *b;
+#endif
 	struct btree_iter_set {
 		struct bkey *k, *end;
 	} data[MAX_BSETS];
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index aba787d954e5..fa4d0b1f6d75 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -216,6 +216,10 @@ static void bch_btree_node_read_done(struct btree *b)
 	iter->size = b->c->sb.bucket_size / b->c->sb.block_size;
 	iter->used = 0;
 
+#ifdef CONFIG_BCACHE_DEBUG
+	iter->b = b;
+#endif
+
 	if (!i->seq)
 		goto err;
 
@@ -454,7 +458,7 @@ void bch_btree_node_write(struct btree *b, struct closure *parent)
 	BUG_ON(b->written >= btree_blocks(b));
 	BUG_ON(b->written && !i->keys);
 	BUG_ON(b->sets->data->seq != i->seq);
-	bch_check_key_order(b, i);
+	bch_check_keys(b, "writing");
 
 	cancel_delayed_work(&b->work);
 
@@ -1917,7 +1921,7 @@ static bool bch_btree_insert_keys(struct btree *b, struct btree_op *op,
 				  struct bkey *replace_key)
 {
 	bool ret = false;
-	unsigned oldsize = bch_count_data(b);
+	int oldsize = bch_count_data(b);
 
 	while (!bch_keylist_empty(insert_keys)) {
 		struct bset *i = write_block(b);
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 8fc1e8925399..27e90b189112 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -259,14 +259,6 @@ static inline void rw_lock(bool w, struct btree *b, int level)
 
 static inline void rw_unlock(bool w, struct btree *b)
 {
-#ifdef CONFIG_BCACHE_EDEBUG
-	unsigned i;
-
-	if (w && b->key.ptr[0])
-		for (i = 0; i <= b->nsets; i++)
-			bch_check_key_order(b, b->sets[i].data);
-#endif
-
 	if (w)
 		b->seq++;
 	(w ? up_write : up_read)(&b->lock);
diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index d9ccb3169aa2..e99e6b8852b2 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c
@@ -76,29 +76,17 @@ int bch_bkey_to_text(char *buf, size_t size, const struct bkey *k)
 	return out - buf;
 }
 
-int bch_btree_to_text(char *buf, size_t size, const struct btree *b)
-{
-	return scnprintf(buf, size, "%zu level %i/%i",
-			 PTR_BUCKET_NR(b->c, &b->key, 0),
-			 b->level, b->c->root ? b->c->root->level : -1);
-}
-
-#if defined(CONFIG_BCACHE_DEBUG) || defined(CONFIG_BCACHE_EDEBUG)
-
-static bool skipped_backwards(struct btree *b, struct bkey *k)
-{
-	return bkey_cmp(k, (!b->level)
-			? &START_KEY(bkey_next(k))
-			: bkey_next(k)) > 0;
-}
+#ifdef CONFIG_BCACHE_DEBUG
 
 static void dump_bset(struct btree *b, struct bset *i)
 {
-	struct bkey *k;
+	struct bkey *k, *next;
 	unsigned j;
 	char buf[80];
 
-	for (k = i->start; k < end(i); k = bkey_next(k)) {
+	for (k = i->start; k < end(i); k = next) {
+		next = bkey_next(k);
+
 		bch_bkey_to_text(buf, sizeof(buf), k);
 		printk(KERN_ERR "block %zu key %zi/%u: %s", index(i, b),
 		       (uint64_t *) k - i->d, i->keys, buf);
@@ -114,15 +102,21 @@ static void dump_bset(struct btree *b, struct bset *i)
 
 		printk(" %s\n", bch_ptr_status(b->c, k));
 
-		if (bkey_next(k) < end(i) &&
-		    skipped_backwards(b, k))
+		if (next < end(i) &&
+		    bkey_cmp(k, !b->level ? &START_KEY(next) : next) > 0)
 			printk(KERN_ERR "Key skipped backwards\n");
 	}
 }
 
-#endif
+static void bch_dump_bucket(struct btree *b)
+{
+	unsigned i;
 
-#ifdef CONFIG_BCACHE_DEBUG
+	console_lock();
+	for (i = 0; i <= b->nsets; i++)
+		dump_bset(b, b->sets[i].data);
+	console_unlock();
+}
 
 void bch_btree_verify(struct btree *b, struct bset *new)
 {
@@ -211,11 +205,7 @@ out_put:
 	bio_put(check);
 }
 
-#endif
-
-#ifdef CONFIG_BCACHE_EDEBUG
-
-unsigned bch_count_data(struct btree *b)
+int __bch_count_data(struct btree *b)
 {
 	unsigned ret = 0;
 	struct btree_iter iter;
@@ -227,72 +217,60 @@ unsigned bch_count_data(struct btree *b)
 	return ret;
 }
 
-static void vdump_bucket_and_panic(struct btree *b, const char *fmt,
-				   va_list args)
-{
-	unsigned i;
-	char buf[80];
-
-	console_lock();
-
-	for (i = 0; i <= b->nsets; i++)
-		dump_bset(b, b->sets[i].data);
-
-	vprintk(fmt, args);
-
-	console_unlock();
-
-	bch_btree_to_text(buf, sizeof(buf), b);
-	panic("at %s\n", buf);
-}
-
-void bch_check_key_order_msg(struct btree *b, struct bset *i,
-			     const char *fmt, ...)
-{
-	struct bkey *k;
-
-	if (!i->keys)
-		return;
-
-	for (k = i->start; bkey_next(k) < end(i); k = bkey_next(k))
-		if (skipped_backwards(b, k)) {
-			va_list args;
-			va_start(args, fmt);
-
-			vdump_bucket_and_panic(b, fmt, args);
-			va_end(args);
-		}
-}
-
-void bch_check_keys(struct btree *b, const char *fmt, ...)
+void __bch_check_keys(struct btree *b, const char *fmt, ...)
 {
 	va_list args;
 	struct bkey *k, *p = NULL;
 	struct btree_iter iter;
-
-	if (b->level)
-		return;
+	const char *err;
 
 	for_each_key(b, k, &iter) {
-		if (p && bkey_cmp(&START_KEY(p), &START_KEY(k)) > 0) {
-			printk(KERN_ERR "Keys out of order:\n");
-			goto bug;
-		}
+		if (!b->level) {
+			err = "Keys out of order";
+			if (p && bkey_cmp(&START_KEY(p), &START_KEY(k)) > 0)
+				goto bug;
 
-		if (bch_ptr_invalid(b, k))
-			continue;
+			if (bch_ptr_invalid(b, k))
+				continue;
 
-		if (p && bkey_cmp(p, &START_KEY(k)) > 0) {
-			printk(KERN_ERR "Overlapping keys:\n");
-			goto bug;
+			err =  "Overlapping keys";
+			if (p && bkey_cmp(p, &START_KEY(k)) > 0)
+				goto bug;
+		} else {
+			if (bch_ptr_bad(b, k))
+				continue;
+
+			err = "Duplicate keys";
+			if (p && !bkey_cmp(p, k))
+				goto bug;
 		}
 		p = k;
 	}
+
+	err = "Key larger than btree node key";
+	if (p && bkey_cmp(p, &b->key) > 0)
+		goto bug;
+
 	return;
 bug:
+	bch_dump_bucket(b);
+
 	va_start(args, fmt);
-	vdump_bucket_and_panic(b, fmt, args);
+	vprintk(fmt, args);
 	va_end(args);
+
+	panic("bcache error: %s:\n", err);
+}
+
+void bch_btree_iter_next_check(struct btree_iter *iter)
+{
+	struct bkey *k = iter->data->k, *next = bkey_next(k);
+
+	if (next < iter->data->end &&
+	    bkey_cmp(k, iter->b->level ? next : &START_KEY(next)) > 0) {
+		bch_dump_bucket(iter->b);
+		panic("Key skipped backwards\n");
+	}
 }
 
 #endif
diff --git a/drivers/md/bcache/debug.h b/drivers/md/bcache/debug.h
index 0f4b3440512c..7914ba0ff316 100644
--- a/drivers/md/bcache/debug.h
+++ b/drivers/md/bcache/debug.h
@@ -4,40 +4,42 @@
 /* Btree/bkey debug printing */
 
 int bch_bkey_to_text(char *buf, size_t size, const struct bkey *k);
-int bch_btree_to_text(char *buf, size_t size, const struct btree *b);
-
-#ifdef CONFIG_BCACHE_EDEBUG
-
-unsigned bch_count_data(struct btree *);
-void bch_check_key_order_msg(struct btree *, struct bset *, const char *, ...);
-void bch_check_keys(struct btree *, const char *, ...);
-
-#define bch_check_key_order(b, i)			\
-	bch_check_key_order_msg(b, i, "keys out of order")
-#define EBUG_ON(cond)		BUG_ON(cond)
-
-#else /* EDEBUG */
-
-#define bch_count_data(b)				0
-#define bch_check_key_order(b, i)			do {} while (0)
-#define bch_check_key_order_msg(b, i, ...)		do {} while (0)
-#define bch_check_keys(b, ...)				do {} while (0)
-#define EBUG_ON(cond)					do {} while (0)
-
-#endif
 
 #ifdef CONFIG_BCACHE_DEBUG
 
 void bch_btree_verify(struct btree *, struct bset *);
 void bch_data_verify(struct cached_dev *, struct bio *);
+int __bch_count_data(struct btree *);
+void __bch_check_keys(struct btree *, const char *, ...);
+void bch_btree_iter_next_check(struct btree_iter *);
+
+#define EBUG_ON(cond)			BUG_ON(cond)
+#define expensive_debug_checks(c)	((c)->expensive_debug_checks)
+#define key_merging_disabled(c)		((c)->key_merging_disabled)
 
 #else /* DEBUG */
 
 static inline void bch_btree_verify(struct btree *b, struct bset *i) {}
-static inline void bch_data_verify(struct cached_dev *dc, struct bio *bio) {};
+static inline void bch_data_verify(struct cached_dev *dc, struct bio *bio) {}
+static inline int __bch_count_data(struct btree *b) { return -1; }
+static inline void __bch_check_keys(struct btree *b, const char *fmt, ...) {}
+static inline void bch_btree_iter_next_check(struct btree_iter *iter) {}
+
+#define EBUG_ON(cond)			do { if (cond); } while (0)
+#define expensive_debug_checks(c)	0
+#define key_merging_disabled(c)		0
 
 #endif
 
+#define bch_count_data(b)						\
+	(expensive_debug_checks((b)->c) ? __bch_count_data(b) : -1)
+
+#define bch_check_keys(b, ...)						\
+do {									\
+	if (expensive_debug_checks((b)->c))				\
+		__bch_check_keys(b, __VA_ARGS__);			\
+} while (0)
+
 #ifdef CONFIG_DEBUG_FS
 void bch_debug_init_cache_set(struct cache_set *);
 #else
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index ab286b9b5e40..9687771ec6f3 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -102,6 +102,7 @@ rw_attribute(io_error_halflife);
 rw_attribute(verify);
 rw_attribute(key_merging_disabled);
 rw_attribute(gc_always_rewrite);
+rw_attribute(expensive_debug_checks);
 rw_attribute(freelist_percent);
 rw_attribute(cache_replacement_policy);
 rw_attribute(btree_shrinker_disabled);
@@ -517,6 +518,8 @@ lock_root:
 	sysfs_print(active_journal_entries,	fifo_used(&c->journal.pin));
 	sysfs_printf(verify,			"%i", c->verify);
 	sysfs_printf(key_merging_disabled,	"%i", c->key_merging_disabled);
+	sysfs_printf(expensive_debug_checks,
+		     "%i", c->expensive_debug_checks);
 	sysfs_printf(gc_always_rewrite,		"%i", c->gc_always_rewrite);
 	sysfs_printf(btree_shrinker_disabled,	"%i", c->shrinker_disabled);
 	sysfs_printf(copy_gc_enabled,		"%i", c->copy_gc_enabled);
@@ -599,6 +602,7 @@ STORE(__bch_cache_set)
 	sysfs_strtoul(journal_delay_ms,		c->journal_delay_ms);
 	sysfs_strtoul(verify,			c->verify);
 	sysfs_strtoul(key_merging_disabled,	c->key_merging_disabled);
+	sysfs_strtoul(expensive_debug_checks,	c->expensive_debug_checks);
 	sysfs_strtoul(gc_always_rewrite,	c->gc_always_rewrite);
 	sysfs_strtoul(btree_shrinker_disabled,	c->shrinker_disabled);
 	sysfs_strtoul(copy_gc_enabled,		c->copy_gc_enabled);
@@ -674,6 +678,7 @@ static struct attribute *bch_cache_set_internal_files[] = {
 #ifdef CONFIG_BCACHE_DEBUG
 	&sysfs_verify,
 	&sysfs_key_merging_disabled,
+	&sysfs_expensive_debug_checks,
 #endif
 	&sysfs_gc_always_rewrite,
 	&sysfs_btree_shrinker_disabled,
diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
index 38ae7a4ce928..8ce5aab55962 100644
--- a/drivers/md/bcache/util.h
+++ b/drivers/md/bcache/util.h
@@ -15,12 +15,12 @@
 
 struct closure;
 
-#ifdef CONFIG_BCACHE_EDEBUG
+#ifdef CONFIG_BCACHE_DEBUG
 
 #define atomic_dec_bug(v)	BUG_ON(atomic_dec_return(v) < 0)
 #define atomic_inc_bug(v, i)	BUG_ON(atomic_inc_return(v) <= i)
 
-#else /* EDEBUG */
+#else /* DEBUG */
 
 #define atomic_dec_bug(v)	atomic_dec(v)
 #define atomic_inc_bug(v, i)	atomic_inc(v)