[Qemu-devel] [PATCH 7/7] block: assign backing relationship in drive-backup

[Fam Zheng]

Assign source image as the backing hd of target bs, so reading target bs
gets the point-in-time copy of data from source image.

Signed-off-by: Fam Zheng <f...@redhat.com>
---
 block/backup.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/block/backup.c b/block/backup.c
index 4e9f927..2dd0540 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -294,6 +294,11 @@ static void coroutine_fn backup_run(void *opaque)
     hbitmap_free(job->bitmap);
 
     bdrv_iostatus_disable(target);
+
+    bdrv_put_ref(target->backing_hd);
+    target->backing_hd = NULL;
+    target->backing_file[0] = '\0';
+    target->backing_format[0] = '\0';
     bdrv_put_ref(target);
 
     block_job_completed(&job->common, ret);
@@ -332,7 +337,15 @@ void backup_start(BlockDriverState *bs, BlockDriverState 
*target,
         return;
     }
 
+    target->backing_hd = bs;
+    pstrcpy(target->backing_file, sizeof(target->backing_file),
+            bs->filename);
+    pstrcpy(target->backing_format, sizeof(target->backing_format),
+            bs->drv->format_name);
     bdrv_get_ref(target);
+    /* Get another ref to source for backing_hd relationship */
+    bdrv_get_ref(bs);
+
     job->on_source_error = on_source_error;
     job->on_target_error = on_target_error;
     job->target = target;
-- 
1.8.3.1