bcache: Debug code improvements

Couple changes:
 * Consolidate bch_check_keys() and bch_check_key_order(), and move the
   checks that only check_key_order() could do to bch_btree_iter_next().

 * Get rid of CONFIG_BCACHE_EDEBUG - now, all that code is compiled in
   when CONFIG_BCACHE_DEBUG is enabled, and there's now a sysfs file to
   flip on the EDEBUG checks at runtime.

 * Dropped an old not terribly useful check in rw_unlock(), and
   refactored/improved a some of the other debug code.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/debug.h b/drivers/md/bcache/debug.h
index 0f4b344..7914ba0 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