block/export: Allocate BlockExport in blk_exp_add()

Instead of letting the driver allocate and return the BlockExport
object, allocate it already in blk_exp_add() and pass it. This allows us
to initialise the generic part before calling into the driver so that
the driver can just use these values instead of having to parse the
options a second time.

For symmetry, move freeing the BlockExport to blk_exp_unref().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-17-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/block/export/export.c b/block/export/export.c
index 8635318ef1..6b2b29078b 100644
--- a/block/export/export.c
+++ b/block/export/export.c
@@ -39,6 +39,8 @@ static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
 {
     const BlockExportDriver *drv;
+    BlockExport *exp;
+    int ret;
 
     drv = blk_exp_find_driver(export->type);
     if (!drv) {
@@ -46,7 +48,20 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
         return NULL;
     }
 
-    return drv->create(export, errp);
+    assert(drv->instance_size >= sizeof(BlockExport));
+    exp = g_malloc0(drv->instance_size);
+    *exp = (BlockExport) {
+        .drv        = drv,
+        .refcount   = 1,
+    };
+
+    ret = drv->create(exp, export, errp);
+    if (ret < 0) {
+        g_free(exp);
+        return NULL;
+    }
+
+    return exp;
 }
 
 /* Callers must hold exp->ctx lock */
@@ -62,6 +77,7 @@ void blk_exp_unref(BlockExport *exp)
     assert(exp->refcount > 0);
     if (--exp->refcount == 0) {
         exp->drv->delete(exp);
+        g_free(exp);
     }
 }