qemu-storage-daemon: Add --export option

Add a --export option to qemu-storage-daemon to export a block node. For
now, only NBD exports are implemented. Apart from the 'type' option
(which is the implied key), it maps the arguments for nbd-server-add to
the command line. Example:

    --export nbd,device=disk,name=test-export,writable=on

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200224143008.13362-12-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 58 insertions, 0 deletions

diff --git a/qapi/block-core.json b/qapi/block-core.json
index cdc585385c..48631218fa 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -5202,6 +5202,33 @@
 { 'command': 'nbd-server-stop' }
 
 ##
+# @BlockExportType:
+#
+# An enumeration of block export types
+#
+# @nbd: NBD export
+#
+# Since: 4.2
+##
+{ 'enum': 'BlockExportType',
+  'data': [ 'nbd' ] }
+
+##
+# @BlockExport:
+#
+# Describes a block export, i.e. how single node should be exported on an
+# external interface.
+#
+# Since: 4.2
+##
+{ 'union': 'BlockExport',
+  'base': { 'type': 'BlockExportType' },
+  'discriminator': 'type',
+  'data': {
+      'nbd': 'BlockExportNbd'
+   } }
+
+##
 # @QuorumOpType:
 #
 # An enumeration of the quorum operation types
diff --git a/qemu-storage-daemon.c b/qemu-storage-daemon.c
index 276a412915..5904d3c5b4 100644
--- a/qemu-storage-daemon.c
+++ b/qemu-storage-daemon.c
@@ -70,6 +70,11 @@ static void help(void)
 "             [,driver specific parameters...]\n"
 "                         configure a block backend\n"
 "\n"
+"  --export [type=]nbd,device=<node-name>[,name=<export-name>]\n"
+"           [,writable=on|off][,bitmap=<name>]\n"
+"                         export the specified block node over NBD\n"
+"                         (requires --nbd-server)\n"
+"\n"
 "  --nbd-server addr.type=inet,addr.host=<host>,addr.port=<port>\n"
 "               [,tls-creds=<id>][,tls-authz=<id>]\n"
 "  --nbd-server addr.type=unix,addr.path=<path>\n"
@@ -91,6 +96,7 @@ QEMU_HELP_BOTTOM "\n",
 
 enum {
     OPTION_BLOCKDEV = 256,
+    OPTION_EXPORT,
     OPTION_NBD_SERVER,
     OPTION_OBJECT,
 };
@@ -104,12 +110,24 @@ static QemuOptsList qemu_object_opts = {
     },
 };
 
+static void init_export(BlockExport *export, Error **errp)
+{
+    switch (export->type) {
+    case BLOCK_EXPORT_TYPE_NBD:
+        qmp_nbd_server_add(&export->u.nbd, errp);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+}
+
 static void process_options(int argc, char *argv[])
 {
     int c;
 
     static const struct option long_options[] = {
         {"blockdev", required_argument, NULL, OPTION_BLOCKDEV},
+        {"export", required_argument, NULL, OPTION_EXPORT},
         {"help", no_argument, NULL, 'h'},
         {"nbd-server", required_argument, NULL, OPTION_NBD_SERVER},
         {"object", required_argument, NULL, OPTION_OBJECT},
@@ -156,6 +174,19 @@ static void process_options(int argc, char *argv[])
                 qapi_free_BlockdevOptions(options);
                 break;
             }
+        case OPTION_EXPORT:
+            {
+                Visitor *v;
+                BlockExport *export;
+
+                v = qobject_input_visitor_new_str(optarg, "type", &error_fatal);
+                visit_type_BlockExport(v, NULL, &export, &error_fatal);
+                visit_free(v);
+
+                init_export(export, &error_fatal);
+                qapi_free_BlockExport(export);
+                break;
+            }
         case OPTION_NBD_SERVER:
             {
                 Visitor *v;