bcache: Convert to lock_cmp_fn

Replace one of bcache's lockdep_set_novalidate_class() usage with the
newly introduced custom lock nesting annotation.

[peterz: changelog]
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Coly Li <colyli@suse.de>
Link: https://lkml.kernel.org/r/20230509195847.1745548-2-kent.overstreet@linux.dev

drivers/md/bcache/btree.c

@@ -559,6 +559,27 @@ static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
 	}
 }
 
+#define cmp_int(l, r)		((l > r) - (l < r))
+
+#ifdef CONFIG_PROVE_LOCKING
+static int btree_lock_cmp_fn(const struct lockdep_map *_a,
+			     const struct lockdep_map *_b)
+{
+	const struct btree *a = container_of(_a, struct btree, lock.dep_map);
+	const struct btree *b = container_of(_b, struct btree, lock.dep_map);
+
+	return -cmp_int(a->level, b->level) ?: bkey_cmp(&a->key, &b->key);
+}
+
+static void btree_lock_print_fn(const struct lockdep_map *map)
+{
+	const struct btree *b = container_of(map, struct btree, lock.dep_map);
+
+	printk(KERN_CONT " l=%u %llu:%llu", b->level,
+	       KEY_INODE(&b->key), KEY_OFFSET(&b->key));
+}
+#endif
+
 static struct btree *mca_bucket_alloc(struct cache_set *c,
 				      struct bkey *k, gfp_t gfp)
 {
@@ -572,7 +593,7 @@ static struct btree *mca_bucket_alloc(struct cache_set *c,
 		return NULL;
 
 	init_rwsem(&b->lock);
-	lockdep_set_novalidate_class(&b->lock);
+	lock_set_cmp_fn(&b->lock, btree_lock_cmp_fn, btree_lock_print_fn);
 	mutex_init(&b->write_lock);
 	lockdep_set_novalidate_class(&b->write_lock);
 	INIT_LIST_HEAD(&b->list);

drivers/md/bcache/btree.h

@@ -247,8 +247,8 @@ static inline void bch_btree_op_init(struct btree_op *op, int write_lock_level)
 
 static inline void rw_lock(bool w, struct btree *b, int level)
 {
-	w ? down_write_nested(&b->lock, level + 1)
-	  : down_read_nested(&b->lock, level + 1);
+	w ? down_write(&b->lock)
+	  : down_read(&b->lock);
 	if (w)
 		b->seq++;
 }