nbd: add nbd start rpc

Multiple nbd disks can be enabled by it. These
created nbd disks can only be running on app start
core at present.
Stop running spdk_nbd_disk by nbd subsystem_fini

Example nbd start rpc request:
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "start_nbd_disk",
  "params": {
    "bdev_name": "AIO1",
    "nbd_device": "/dev/nbd1"
  }
}

Change-Id: I426a10e2fe709f1862e44a7b75318ccb83517b3e
Signed-off-by: Xiaodong Liu <xiaodong.liu@intel.com>
Reviewed-on: https://review.gerrithub.io/390344
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>

lib/nbd/nbd_rpc.c

@@ -39,6 +39,71 @@
 #include "nbd_internal.h"
 #include "spdk_internal/log.h"
 
+struct rpc_start_nbd_disk {
+	char *bdev_name;
+	char *nbd_device;
+};
+
+static void
+free_rpc_start_nbd_disk(struct rpc_start_nbd_disk *req)
+{
+	free(req->bdev_name);
+	free(req->nbd_device);
+}
+
+static const struct spdk_json_object_decoder rpc_start_nbd_disk_decoders[] = {
+	{"bdev_name", offsetof(struct rpc_start_nbd_disk, bdev_name), spdk_json_decode_string},
+	{"nbd_device", offsetof(struct rpc_start_nbd_disk, nbd_device), spdk_json_decode_string},
+};
+
+static void
+spdk_rpc_start_nbd_disk(struct spdk_jsonrpc_request *request,
+			const struct spdk_json_val *params)
+{
+	struct rpc_start_nbd_disk req = {};
+	struct spdk_json_write_ctx *w;
+	struct spdk_nbd_disk *nbd;
+
+	if (spdk_json_decode_object(params, rpc_start_nbd_disk_decoders,
+				    SPDK_COUNTOF(rpc_start_nbd_disk_decoders),
+				    &req)) {
+		SPDK_ERRLOG("spdk_json_decode_object failed\n");
+		goto invalid;
+	}
+
+	if (req.nbd_device == NULL || req.bdev_name == NULL) {
+		goto invalid;
+	}
+
+	/* make sure nbd_device is not registered */
+	nbd = spdk_nbd_disk_find_by_nbd_path(req.nbd_device);
+	if (nbd) {
+		goto invalid;
+	}
+
+	nbd = spdk_nbd_start(req.bdev_name, req.nbd_device);
+	if (!nbd) {
+		goto invalid;
+	}
+
+	free_rpc_start_nbd_disk(&req);
+
+	w = spdk_jsonrpc_begin_result(request);
+	if (w == NULL) {
+		return;
+	}
+
+	spdk_json_write_bool(w, true);
+	spdk_jsonrpc_end_result(request, w);
+	return;
+
+invalid:
+	free_rpc_start_nbd_disk(&req);
+	spdk_jsonrpc_send_error_response(request, SPDK_JSONRPC_ERROR_INVALID_PARAMS, "Invalid parameters");
+}
+
+SPDK_RPC_REGISTER("start_nbd_disk", spdk_rpc_start_nbd_disk)
+
 struct rpc_stop_nbd_disk {
 	char *nbd_device;
 };

scripts/rpc.py

@@ -604,6 +604,18 @@ p = subparsers.add_parser('delete_bdev', help='Delete a blockdev')
 p.add_argument('bdev_name', help='Blockdev name to be deleted. Example: Malloc0.')
 p.set_defaults(func=delete_bdev)
 
+def start_nbd_disk(args):
+    params = {
+        'bdev_name': args.bdev_name,
+        'nbd_device': args.nbd_device
+    }
+    jsonrpc_call('start_nbd_disk', params)
+
+p = subparsers.add_parser('start_nbd_disk', help='Export a bdev as a nbd disk')
+p.add_argument('bdev_name', help='Blockdev name to be exported. Example: Malloc0.')
+p.add_argument('nbd_device', help='Nbd device name to be assigned. Example: /dev/nbd0.')
+p.set_defaults(func=start_nbd_disk)
+
 def stop_nbd_disk(args):
     params = {'nbd_device': args.nbd_device}
     jsonrpc_call('stop_nbd_disk', params)