block: Introduce parents list

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

2 files changed, 5 insertions, 0 deletions

diff --git a/block.c b/block.c
index a2d6238b82..980437f056 100644
--- a/block.c
+++ b/block.c
@@ -1090,6 +1090,7 @@ static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
     };
 
     QLIST_INSERT_HEAD(&parent_bs->children, child, next);
+    QLIST_INSERT_HEAD(&child_bs->parents, child, next_parent);
 
     return child;
 }
@@ -1097,6 +1098,7 @@ static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
 void bdrv_detach_child(BdrvChild *child)
 {
     QLIST_REMOVE(child, next);
+    QLIST_REMOVE(child, next_parent);
     g_free(child);
 }
 
@@ -2038,6 +2040,7 @@ static void bdrv_move_reference_fields(BlockDriverState *bs_dest,
     /* keep the same entry in bdrv_states */
     bs_dest->device_list = bs_src->device_list;
     bs_dest->blk = bs_src->blk;
+    bs_dest->parents = bs_src->parents;
 
     memcpy(bs_dest->op_blockers, bs_src->op_blockers,
            sizeof(bs_dest->op_blockers));
diff --git a/include/block/block_int.h b/include/block/block_int.h
index cfcae52d7d..52ea7c076b 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -339,6 +339,7 @@ struct BdrvChild {
     BlockDriverState *bs;
     const BdrvChildRole *role;
     QLIST_ENTRY(BdrvChild) next;
+    QLIST_ENTRY(BdrvChild) next_parent;
 };
 
 /*
@@ -445,6 +446,7 @@ struct BlockDriverState {
      * parent node of this node. */
     BlockDriverState *inherits_from;
     QLIST_HEAD(, BdrvChild) children;
+    QLIST_HEAD(, BdrvChild) parents;
 
     QDict *options;
     BlockdevDetectZeroesOptions detect_zeroes;