[Qemu-block] [PATCH 1/3] blockdev-backup: Don't move target AioContext if it's attached

[Fam Zheng]

If the BDS is attached, it will want to stay on the AioContext where its
BlockBackend is. Don't call bdrv_set_aio_context in this case.

Signed-off-by: Fam Zheng <address@hidden>
---
 blockdev.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 1892b8e..eb15593 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3376,8 +3376,18 @@ void do_blockdev_backup(const char *device, const char 
*target,
     }
     target_bs = blk_bs(target_blk);
 
+    if (bdrv_get_aio_context(target_bs) != aio_context) {
+        if (!target_bs->blk) {
+            /* The target BDS is not attached, we can safely move it to another
+             * AioContext. */
+            bdrv_set_aio_context(target_bs, aio_context);
+        } else {
+            error_setg(errp, "Target is attached to a different thread from "
+                             "source.");
+            goto out;
+        }
+    }
     bdrv_ref(target_bs);
-    bdrv_set_aio_context(target_bs, aio_context);
     backup_start(bs, target_bs, speed, sync, NULL, on_source_error,
                  on_target_error, block_job_cb, bs, txn, &local_err);
     if (local_err != NULL) {
-- 
2.8.2