[PATCH v7 22/47] block: Use CAF in bdrv_co_rw_vmstate()

[Max Reitz]

If a node whose driver does not provide VM state functions has a
metadata child, the VM state should probably go there; if it is a
filter, the VM state should probably go there.  It follows that we
should generally go down to the primary child.

Signed-off-by: Max Reitz <mre...@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
 block/io.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 37057f13e0..9e802804bb 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2646,6 +2646,7 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector 
*qiov, int64_t pos,
                    bool is_read)
 {
     BlockDriver *drv = bs->drv;
+    BlockDriverState *child_bs = bdrv_primary_bs(bs);
     int ret = -ENOTSUP;
 
     bdrv_inc_in_flight(bs);
@@ -2658,8 +2659,8 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector 
*qiov, int64_t pos,
         } else {
             ret = drv->bdrv_save_vmstate(bs, qiov, pos);
         }
-    } else if (bs->file) {
-        ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
+    } else if (child_bs) {
+        ret = bdrv_co_rw_vmstate(child_bs, qiov, pos, is_read);
     }
 
     bdrv_dec_in_flight(bs);
-- 
2.26.2