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>

1 files changed, 14 insertions, 1 deletions

diff --git a/nbd/server.c b/nbd/server.c
index bd53f7baea..f5af93c253 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -18,6 +18,8 @@
  */
 
 #include "qemu/osdep.h"
+
+#include "block/export.h"
 #include "qapi/error.h"
 #include "qemu/queue.h"
 #include "trace.h"
@@ -80,6 +82,7 @@ struct NBDRequestData {
 };
 
 struct NBDExport {
+    BlockExport common;
     int refcount;
     void (*close)(NBDExport *exp);
 
@@ -1512,10 +1515,15 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
 {
     AioContext *ctx;
     BlockBackend *blk;
-    NBDExport *exp = g_new0(NBDExport, 1);
+    NBDExport *exp;
     uint64_t perm;
     int ret;
 
+    exp = g_new0(NBDExport, 1);
+    exp->common = (BlockExport) {
+        .drv = &blk_exp_nbd,
+    };
+
     /*
      * NBD exports are used for non-shared storage migration.  Make sure
      * that BDRV_O_INACTIVE is cleared and the image is ready for write
@@ -1731,6 +1739,11 @@ void nbd_export_put(NBDExport *exp)
     }
 }
 
+const BlockExportDriver blk_exp_nbd = {
+    .type               = BLOCK_EXPORT_TYPE_NBD,
+    .create             = nbd_export_create,
+};
+
 void nbd_export_close_all(void)
 {
     NBDExport *exp, *next;