block/export: Add BlockExport infrastructure and block-export-add

We want to have a common set of commands for all types of block exports.
Currently, this is only NBD, but we're going to add more types.

This patch adds the basic BlockExport and BlockExportDriver structs and
a QMP command block-export-add that creates a new export based on the
given BlockExportOptions.

qmp_nbd_server_add() becomes a wrapper around qmp_block_export_add().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-5-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

3 files changed, 51 insertions, 0 deletions

diff --git a/block/export/export.c b/block/export/export.c
new file mode 100644
index 0000000..fd65541
--- /dev/null
+++ b/block/export/export.c
@@ -0,0 +1,48 @@
+/*
+ * Common block export infrastructure
+ *
+ * Copyright (c) 2012, 2020 Red Hat, Inc.
+ *
+ * Authors:
+ * Paolo Bonzini <pbonzini@redhat.com>
+ * Kevin Wolf <kwolf@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/export.h"
+#include "block/nbd.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-block-export.h"
+
+static const BlockExportDriver *blk_exp_drivers[] = {
+    &blk_exp_nbd,
+};
+
+static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
+        if (blk_exp_drivers[i]->type == type) {
+            return blk_exp_drivers[i];
+        }
+    }
+    return NULL;
+}
+
+void qmp_block_export_add(BlockExportOptions *export, Error **errp)
+{
+    const BlockExportDriver *drv;
+
+    drv = blk_exp_find_driver(export->type);
+    if (!drv) {
+        error_setg(errp, "No driver found for the requested export type");
+        return;
+    }
+
+    drv->create(export, errp);
+}
diff --git a/block/export/meson.build b/block/export/meson.build
new file mode 100644
index 0000000..558ef35
--- /dev/null
+++ b/block/export/meson.build
@@ -0,0 +1 @@
+block_ss.add(files('export.c'))
diff --git a/block/meson.build b/block/meson.build
index a3e56b7..0b38dc3 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -110,6 +110,8 @@ block_ss.add(module_block_h)
 block_ss.add(files('stream.c'))
 
 softmmu_ss.add(files('qapi-sysemu.c'))
+
+subdir('export')
 subdir('monitor')
 
 modules += {'block': block_modules}