qemu-nbd: Use blk_exp_add() to create the export

With this change, NBD exports are now only created through the
BlockExport interface. This allows us finally to move things from the
NBD layer to the BlockExport layer if they make sense for other export
types, too.

blk_exp_add() returns only a weak reference, so the explicit
nbd_export_put() goes away.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-12-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

3 files changed, 30 insertions, 7 deletions

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 3a51b3e..7bb0b09 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -28,9 +28,15 @@ typedef struct NBDServerData {
 } NBDServerData;
 
 static NBDServerData *nbd_server;
+static bool is_qemu_nbd;
 
 static void nbd_update_server_watch(NBDServerData *s);
 
+void nbd_server_is_qemu_nbd(bool value)
+{
+    is_qemu_nbd = value;
+}
+
 static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
 {
     nbd_client_put(client);
@@ -176,7 +182,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
 
     assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD);
 
-    if (!nbd_server) {
+    if (!nbd_server && !is_qemu_nbd) {
         error_setg(errp, "NBD server not running");
         return NULL;
     }
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 9449b3d..1dafe70 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -352,6 +352,7 @@ void nbd_client_new(QIOChannelSocket *sioc,
 void nbd_client_get(NBDClient *client);
 void nbd_client_put(NBDClient *client);
 
+void nbd_server_is_qemu_nbd(bool value);
 void nbd_server_start(SocketAddress *addr, const char *tls_creds,
                       const char *tls_authz, uint32_t max_connections,
                       Error **errp);
diff --git a/qemu-nbd.c b/qemu-nbd.c
index abbed8f..fc6e68a 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -65,7 +65,6 @@
 
 #define MBR_SIZE 512
 
-static NBDExport *export;
 static int verbose;
 static char *srcpath;
 static SocketAddress *saddr;
@@ -580,6 +579,7 @@ int main(int argc, char **argv)
     int old_stderr = -1;
     unsigned socket_activation;
     const char *pid_file_name = NULL;
+    BlockExportOptions *export_opts;
 
 #if HAVE_NBD_DEVICE
     /* The client thread uses SIGTERM to interrupt the server.  A signal
@@ -1059,9 +1059,27 @@ int main(int argc, char **argv)
 
     bs->detect_zeroes = detect_zeroes;
 
-    export = nbd_export_new(bs, export_name,
-                            export_description, bitmap, readonly, shared > 1,
-                            writethrough, &error_fatal);
+    nbd_server_is_qemu_nbd(true);
+
+    export_opts = g_new(BlockExportOptions, 1);
+    *export_opts = (BlockExportOptions) {
+        .type               = BLOCK_EXPORT_TYPE_NBD,
+        .has_writethrough   = true,
+        .writethrough       = writethrough,
+        .u.nbd = {
+            .device             = g_strdup(bdrv_get_node_name(bs)),
+            .has_name           = true,
+            .name               = g_strdup(export_name),
+            .has_description    = !!export_description,
+            .description        = g_strdup(export_description),
+            .has_writable       = true,
+            .writable           = !readonly,
+            .has_bitmap         = !!bitmap,
+            .bitmap             = g_strdup(bitmap),
+        },
+    };
+    blk_exp_add(export_opts, &error_fatal);
+    qapi_free_BlockExportOptions(export_opts);
 
     if (device) {
 #if HAVE_NBD_DEVICE
@@ -1101,9 +1119,7 @@ int main(int argc, char **argv)
     do {
         main_loop_wait(false);
         if (state == TERMINATE) {
-            nbd_export_put(export);
             nbd_export_close_all();
-            export = NULL;
             state = TERMINATED;
         }
     } while (state != TERMINATED);