Fix race condition during cache attach

After attaching new cache device handle all the IOs in Pass-Through mode
until all the d2c requests are completed.

Signed-off-by: Robert Baldyga <robert.baldyga@huawei.com>

src/engine/cache_engine.c

@@ -162,6 +162,11 @@ void ocf_resolve_effective_cache_mode(ocf_cache_t cache,
 		return;
 	}
 
+	if (env_atomic_read(&cache->attach_pt)) {
+		req->cache_mode = ocf_req_cache_mode_pt;
+		return;
+	}
+
 	if (cache->pt_unaligned_io && !ocf_req_is_4k(req->addr, req->bytes)) {
 		req->cache_mode = ocf_req_cache_mode_pt;
 		return;

src/mngt/ocf_mngt_cache.c

@@ -1901,18 +1901,35 @@ static void _ocf_mngt_attach_shutdown_status(ocf_pipeline_t pipeline,
 		_ocf_mngt_attach_shutdown_status_complete, context);
 }
 
+
+static void _ocf_mngt_attach_post_init_finish(void *priv)
+{
+	struct ocf_cache_attach_context *context = priv;
+	ocf_cache_t cache = context->cache;
+
+	ocf_refcnt_unfreeze(&cache->refcnt.d2c);
+
+	env_atomic_set(&cache->attach_pt, 0);
+
+	ocf_cache_log(cache, log_debug, "Cache attached\n");
+
+	ocf_pipeline_next(context->pipeline);
+}
+
 static void _ocf_mngt_attach_post_init(ocf_pipeline_t pipeline,
 		void *priv, ocf_pipeline_arg_t arg)
 {
 	struct ocf_cache_attach_context *context = priv;
 	ocf_cache_t cache = context->cache;
 
+	env_atomic_set(&cache->attach_pt, 1);
+
 	ocf_cleaner_refcnt_unfreeze(cache);
 	ocf_refcnt_unfreeze(&cache->refcnt.metadata);
 
-	ocf_cache_log(cache, log_debug, "Cache attached\n");
+	ocf_refcnt_freeze(&cache->refcnt.d2c);
-
+	ocf_refcnt_register_zero_cb(&cache->refcnt.d2c,
-	ocf_pipeline_next(pipeline);
+			_ocf_mngt_attach_post_init_finish, context);
 }
 
 static void _ocf_mngt_attach_handle_error(

src/ocf_cache_priv.h

@@ -106,6 +106,8 @@ struct ocf_cache {
 	env_atomic flush_in_progress;
 	env_mutex flush_mutex;
 
+	env_atomic attach_pt;
+
 	struct ocf_cleaner cleaner;
 
 	struct list_head io_queues;