block-backend: Add blk_set_bs()

It allows changing the BlockDriverState that a BlockBackend points to.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/block/block-backend.c b/block/block-backend.c
index c2e8732..2256551 100644 (file)
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -239,6 +239,23 @@ BlockDriverState *blk_bs(BlockBackend *blk)
 }
 
 /*
+ * Changes the BlockDriverState attached to @blk
+ */
+void blk_set_bs(BlockBackend *blk, BlockDriverState *bs)
+{
+    bdrv_ref(bs);
+
+    if (blk->bs) {
+        blk->bs->blk = NULL;
+        bdrv_unref(blk->bs);
+    }
+    assert(bs->blk == NULL);
+
+    blk->bs = bs;
+    bs->blk = blk;
+}
+
+/*
  * Return @blk's DriveInfo if any, else null.
  */
 DriveInfo *blk_legacy_dinfo(BlockBackend *blk)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 4598101..cfcae52 100644 (file)
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -659,6 +659,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
                   BlockCompletionFunc *cb, void *opaque,
                   Error **errp);
 
+void blk_set_bs(BlockBackend *blk, BlockDriverState *bs);
+
 void blk_dev_change_media_cb(BlockBackend *blk, bool load);
 bool blk_dev_has_removable_media(BlockBackend *blk);
 void blk_dev_eject_request(BlockBackend *blk, bool force);