block/export: Add node-name to BlockExportOptions

Every block export needs a block node to export, so add a 'node-name'
option to BlockExportOptions and remove the replaced option 'device'
from BlockExportOptionsNbd.

To maintain compatibility in nbd-server-add, BlockExportOptionsNbd needs
to be wrapped by a new type NbdServerAddOptions that adds 'device' back
because nbd-server-add doesn't use the BlockExportOptions base type at
all (so even without changing it to a 'node-name' option in
block-export-add, this compatibility code would be necessary).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-16-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/monitor/block-hmp-cmds.c

@@ -398,7 +398,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
     Error *local_err = NULL;
     BlockInfoList *block_list, *info;
     SocketAddress *addr;
-    BlockExportOptionsNbd export;
+    NbdServerAddOptions export;
 
     if (writable && !all) {
         error_setg(&local_err, "-w only valid together with -a");
@@ -431,7 +431,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
             continue;
         }
 
-        export = (BlockExportOptionsNbd) {
+        export = (NbdServerAddOptions) {
             .device         = info->value->device,
             .has_writable   = true,
             .writable       = writable,
@@ -458,7 +458,7 @@ void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
     bool writable = qdict_get_try_bool(qdict, "writable", false);
     Error *local_err = NULL;
 
-    BlockExportOptionsNbd export = {
+    NbdServerAddOptions export = {
         .device         = (char *) device,
         .has_name       = !!name,
         .name           = (char *) name,

blockdev-nbd.c

@@ -188,7 +188,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
     }
 
     if (!arg->has_name) {
-        arg->name = arg->device;
+        arg->name = exp_args->node_name;
     }
 
     if (strlen(arg->name) > NBD_MAX_STRING_SIZE) {
@@ -206,7 +206,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
         return NULL;
     }
 
-    bs = bdrv_lookup_bs(arg->device, arg->device, errp);
+    bs = bdrv_lookup_bs(NULL, exp_args->node_name, errp);
     if (!bs) {
         return NULL;
     }
@@ -244,21 +244,40 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp)
     return (BlockExport*) exp;
 }
 
-void qmp_nbd_server_add(BlockExportOptionsNbd *arg, Error **errp)
+void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
 {
     BlockExport *export;
     BlockDriverState *bs;
     BlockBackend *on_eject_blk;
-    BlockExportOptions export_opts;
+    BlockExportOptions *export_opts;
 
     bs = bdrv_lookup_bs(arg->device, arg->device, errp);
     if (!bs) {
         return;
     }
 
-    export_opts = (BlockExportOptions) {
+    /*
+     * block-export-add would default to the node-name, but we may have to use
+     * the device name as a default here for compatibility.
+     */
+    if (!arg->has_name) {
+        arg->name = arg->device;
+    }
+
+    export_opts = g_new(BlockExportOptions, 1);
+    *export_opts = (BlockExportOptions) {
         .type                   = BLOCK_EXPORT_TYPE_NBD,
-        .u.nbd = *arg,
+        .node_name              = g_strdup(bdrv_get_node_name(bs)),
+        .u.nbd = {
+            .has_name           = true,
+            .name               = g_strdup(arg->name),
+            .has_description    = arg->has_description,
+            .description        = g_strdup(arg->description),
+            .has_writable       = arg->has_writable,
+            .writable           = arg->writable,
+            .has_bitmap         = arg->has_bitmap,
+            .bitmap             = g_strdup(arg->bitmap),
+        },
     };
 
     /*
@@ -267,13 +286,13 @@ void qmp_nbd_server_add(BlockExportOptionsNbd *arg, Error **errp)
      * block-export-add.
      */
     if (bdrv_is_read_only(bs)) {
-        export_opts.u.nbd.has_writable = true;
+        export_opts->u.nbd.has_writable = true;
-        export_opts.u.nbd.writable = false;
+        export_opts->u.nbd.writable = false;
     }
 
-    export = blk_exp_add(&export_opts, errp);
+    export = blk_exp_add(export_opts, errp);
     if (!export) {
-        return;
+        goto fail;
     }
 
     /*
@@ -284,6 +303,9 @@ void qmp_nbd_server_add(BlockExportOptionsNbd *arg, Error **errp)
     if (on_eject_blk) {
         nbd_export_set_on_eject_blk(export, on_eject_blk);
     }
+
+fail:
+    qapi_free_BlockExportOptions(export_opts);
 }
 
 void qmp_nbd_server_remove(const char *name,

qapi/block-export.json

@@ -65,9 +65,8 @@
 ##
 # @BlockExportOptionsNbd:
 #
-# An NBD block export.
+# An NBD block export (options shared between nbd-server-add and the NBD branch
-#
+# of block-export-add).
-# @device: The device name or node name of the node to be exported
 #
 # @name: Export name. If unspecified, the @device parameter is used as the
 #        export name. (Since 2.12)
@@ -85,9 +84,22 @@
 # Since: 5.0
 ##
 { 'struct': 'BlockExportOptionsNbd',
-  'data': {'device': 'str', '*name': 'str', '*description': 'str',
+  'data': { '*name': 'str', '*description': 'str',
             '*writable': 'bool', '*bitmap': 'str' } }
 
+##
+# @NbdServerAddOptions:
+#
+# An NBD block export.
+#
+# @device: The device name or node name of the node to be exported
+#
+# Since: 5.0
+##
+{ 'struct': 'NbdServerAddOptions',
+  'base': 'BlockExportOptionsNbd',
+  'data': { 'device': 'str' } }
+
 ##
 # @nbd-server-add:
 #
@@ -99,7 +111,7 @@
 # Since: 1.3.0
 ##
 { 'command': 'nbd-server-add',
-  'data': 'BlockExportOptionsNbd', 'boxed': true }
+  'data': 'NbdServerAddOptions', 'boxed': true }
 
 ##
 # @NbdServerRemoveMode:
@@ -170,6 +182,8 @@
 # Describes a block export, i.e. how single node should be exported on an
 # external interface.
 #
+# @node-name: The node name of the block node to be exported (since: 5.2)
+#
 # @writethrough: If true, caches are flushed after every write request to the
 #                export before completion is signalled. (since: 5.2;
 #                default: false)
@@ -178,6 +192,7 @@
 ##
 { 'union': 'BlockExportOptions',
   'base': { 'type': 'BlockExportType',
+            'node-name': 'str',
             '*writethrough': 'bool' },
   'discriminator': 'type',
   'data': {

qemu-nbd.c

@@ -1064,10 +1064,10 @@ int main(int argc, char **argv)
     export_opts = g_new(BlockExportOptions, 1);
     *export_opts = (BlockExportOptions) {
         .type               = BLOCK_EXPORT_TYPE_NBD,
+        .node_name          = g_strdup(bdrv_get_node_name(bs)),
         .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,