ublk: add an rpc method to get current ublk devices

Signed-off-by: Yifan Bian <yifan.bian@intel.com>
Co-authored-by: Xiaodong Liu <xiaodong.liu@intel.com>
Change-Id: I3fdf9795b90d7a30478ba81d8144bbf2f1cbdd2a
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/15987
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Xiaodong Liu <xiaodong.liu@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>

CHANGELOG.md

@@ -176,6 +176,15 @@ For the active-active policy of the multipath mode, in addition to the default r
 selector, the minimum queue depth path selector was added. The minimum queue depth path selector
 selects an I/O path according to the number of outstanding requests of each nvme qpair.
 
+### ublk device
+
+The ublk application supports the ublk kernel driver. It's implemented as a ublk backend
+in spdk_tgt and could be started with specifying configuration. See the
+[ublk](https://www.kernel.org/doc/html/latest/block/ublk.html) documentation for more details.
+
+ublk bdev could export a block device via Linux ublk. It will move this backend device into userspace
+as `/dev/ublkb*`. Before to adding ublk device, need to create ublk target by rpc methond.
+
 ## v22.09
 
 ### accel

doc/jsonrpc.md

@@ -10831,6 +10831,50 @@ Example response:
 }
 ~~~
 
+### ublk_get_disks {#rpc_ublk_get_disks}
+
+Display full or specified ublk device list
+
+#### Parameters
+
+Name                    | Optional | Type        | Description
+----------------------- | -------- | ----------- | -----------
+ublk_id                 | Optional | int         | ublk device id to display
+
+#### Response
+
+Display ublk device list
+
+#### Example
+
+Example request:
+
+~~~json
+{
+  "jsonrpc": "2.0",
+  "method": "ublk_get_disks",
+  "id": 1
+}
+~~~
+
+Example response:
+
+~~~json
+{
+  "jsonrpc": "2.0",
+  "id": 1,
+  "result":  [
+    {
+      "ublk_device": "/dev/ublkb1",
+      "id": 1,
+      "queue_depth": 512,
+      "num_queues": 1,
+      "bdev_name": "Malloc1"
+    }
+  ]
+}
+~~~
+
 ## Linux Network Block Device (NBD) {#jsonrpc_components_nbd}
 
 SPDK supports exporting bdevs through Linux nbd. These devices then appear as standard Linux kernel block devices

lib/ublk/ublk.c

@@ -561,6 +561,34 @@ ublk_dev_find_by_id(uint32_t ublk_id)
 	return NULL;
 }
 
+uint32_t
+ublk_dev_get_id(struct spdk_ublk_dev *ublk)
+{
+	return ublk->ublk_id;
+}
+
+struct spdk_ublk_dev *ublk_dev_first(void)
+{
+	return TAILQ_FIRST(&g_ublk_bdevs);
+}
+
+struct spdk_ublk_dev *ublk_dev_next(struct spdk_ublk_dev *prev)
+{
+	return TAILQ_NEXT(prev, tailq);
+}
+
+uint32_t
+ublk_dev_get_queue_depth(struct spdk_ublk_dev *ublk)
+{
+	return ublk->queue_depth;
+}
+
+uint32_t
+ublk_dev_get_num_queues(struct spdk_ublk_dev *ublk)
+{
+	return ublk->num_queues;
+}
+
 const char *
 ublk_dev_get_bdev_name(struct spdk_ublk_dev *ublk)
 {

lib/ublk/ublk_internal.h

@@ -25,7 +25,12 @@ int ublk_start_disk(const char *bdev_name, uint32_t ublk_id,
 		    uint32_t num_queues, uint32_t queue_depth);
 int ublk_stop_disk(uint32_t ublk_id, ublk_del_cb del_cb, void *cb_arg);
 struct spdk_ublk_dev *ublk_dev_find_by_id(uint32_t ublk_id);
+uint32_t ublk_dev_get_id(struct spdk_ublk_dev *ublk);
 const char *ublk_dev_get_bdev_name(struct spdk_ublk_dev *ublk);
+struct spdk_ublk_dev *ublk_dev_first(void);
+struct spdk_ublk_dev *ublk_dev_next(struct spdk_ublk_dev *prev);
+uint32_t ublk_dev_get_queue_depth(struct spdk_ublk_dev *ublk);
+uint32_t ublk_dev_get_num_queues(struct spdk_ublk_dev *ublk);
 
 #ifdef __cplusplus
 }

lib/ublk/ublk_rpc.c

@@ -187,3 +187,75 @@ invalid:
 }
 
 SPDK_RPC_REGISTER("ublk_stop_disk", rpc_ublk_stop_disk, SPDK_RPC_RUNTIME)
+
+static void
+rpc_dump_ublk_info(struct spdk_json_write_ctx *w,
+		   struct spdk_ublk_dev *ublk)
+{
+	char ublk_path[32];
+
+	snprintf(ublk_path, 32, "%s%u", "/dev/ublkb", ublk_dev_get_id(ublk));
+	spdk_json_write_object_begin(w);
+
+	spdk_json_write_named_string(w, "ublk_device", ublk_path);
+	spdk_json_write_named_uint32(w, "id", ublk_dev_get_id(ublk));
+	spdk_json_write_named_uint32(w, "queue_depth", ublk_dev_get_queue_depth(ublk));
+	spdk_json_write_named_uint32(w, "num_queues", ublk_dev_get_num_queues(ublk));
+	spdk_json_write_named_string(w, "bdev_name", ublk_dev_get_bdev_name(ublk));
+
+	spdk_json_write_object_end(w);
+}
+
+struct rpc_ublk_get_disks {
+	uint32_t ublk_id;
+};
+
+static const struct spdk_json_object_decoder rpc_ublk_get_disks_decoders[] = {
+	{"ublk_id", offsetof(struct rpc_ublk_get_disks, ublk_id), spdk_json_decode_uint32, true},
+};
+
+static void
+rpc_ublk_get_disks(struct spdk_jsonrpc_request *request,
+		   const struct spdk_json_val *params)
+{
+	struct rpc_ublk_get_disks req = {};
+	struct spdk_json_write_ctx *w;
+	struct spdk_ublk_dev *ublk = NULL;
+
+	if (params != NULL) {
+		if (spdk_json_decode_object(params, rpc_ublk_get_disks_decoders,
+					    SPDK_COUNTOF(rpc_ublk_get_disks_decoders),
+					    &req)) {
+			SPDK_ERRLOG("spdk_json_decode_object failed\n");
+			spdk_jsonrpc_send_error_response(request, SPDK_JSONRPC_ERROR_INTERNAL_ERROR,
+							 "spdk_json_decode_object failed");
+			return;
+		}
+
+		if (req.ublk_id) {
+			ublk = ublk_dev_find_by_id(req.ublk_id);
+			if (ublk == NULL) {
+				SPDK_ERRLOG("ublk device '%d' does not exist\n", req.ublk_id);
+				spdk_jsonrpc_send_error_response(request, -ENODEV, spdk_strerror(ENODEV));
+				return;
+			}
+		}
+	}
+
+	w = spdk_jsonrpc_begin_result(request);
+	spdk_json_write_array_begin(w);
+
+	if (ublk != NULL) {
+		rpc_dump_ublk_info(w, ublk);
+	} else {
+		for (ublk = ublk_dev_first(); ublk != NULL; ublk = ublk_dev_next(ublk)) {
+			rpc_dump_ublk_info(w, ublk);
+		}
+	}
+
+	spdk_json_write_array_end(w);
+	spdk_jsonrpc_end_result(request, w);
+
+	return;
+}
+SPDK_RPC_REGISTER("ublk_get_disks", rpc_ublk_get_disks, SPDK_RPC_RUNTIME)

python/spdk/rpc/ublk.py

@@ -28,3 +28,10 @@ def ublk_start_disk(client, bdev_name, ublk_id=1, num_queues=1, queue_depth=128)
 def ublk_stop_disk(client, ublk_id=1):
     params = {'ublk_id': ublk_id}
     return client.call('ublk_stop_disk', params)
+
+
+def ublk_get_disks(client, ublk_id=1):
+    params = {}
+    if ublk_id:
+        params['ublk_id'] = ublk_id
+    return client.call('ublk_get_disks', params)

scripts/rpc.py

@@ -2260,6 +2260,15 @@ Format: 'user:u1 secret:s1 muser:mu1 msecret:ms1,user:u2 secret:s2 muser:mu2 mse
     p.add_argument('ublk_id', help='ublk device id to be deleted. Example: 1.', type=int)
     p.set_defaults(func=ublk_stop_disk)
 
+    def ublk_get_disks(args):
+        print_dict(rpc.ublk.ublk_get_disks(args.client,
+                                           ublk_id=args.ublk_id))
+
+    p = subparsers.add_parser('ublk_get_disks',
+                              help='Display full or specified ublk device list')
+    p.add_argument('-n', '--ublk-id', help="ublk device id. Example: 1", type=int, required=False)
+    p.set_defaults(func=ublk_get_disks)
+
     # nbd
     def nbd_start_disk(args):
         print(rpc.nbd.nbd_start_disk(args.client,