block: Add list of children to BlockDriverState

This allows iterating over all children of a given BDS, not only
including bs->file and bs->backing_hd, but also driver-specific
ones like VMDK extents or Quorum children.

For bdrv_swap(), the list of children of the swapped BDS stays at that
BDS (because that's where the pointers stay as well). The list head
moves and pointers to it must be fixed up therefore.

The list of children in the parent of the swapped BDS is not affected by
the swap. The contents of the BDS objects is swapped, so the existing
pointer in the parent automatically points to the newly swapped in BDS.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/block.c b/block.c
index 9a860f12c7..209ba39d31 100644
--- a/block.c
+++ b/block.c
@@ -1325,6 +1325,19 @@ out:
     return ret;
 }
 
+static void bdrv_attach_child(BlockDriverState *parent_bs,
+                              BlockDriverState *child_bs,
+                              const BdrvChildRole *child_role)
+{
+    BdrvChild *child = g_new(BdrvChild, 1);
+    *child = (BdrvChild) {
+        .bs     = child_bs,
+        .role   = child_role,
+    };
+
+    QLIST_INSERT_HEAD(&parent_bs->children, child, next);
+}
+
 /*
  * Opens a disk image (raw, qcow2, vmdk, ...)
  *
@@ -1377,6 +1390,9 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
             return -ENODEV;
         }
         bdrv_ref(bs);
+        if (child_role) {
+            bdrv_attach_child(parent, bs, child_role);
+        }
         *pbs = bs;
         return 0;
     }
@@ -1520,6 +1536,10 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
         goto close_and_fail;
     }
 
+    if (child_role) {
+        bdrv_attach_child(parent, bs, child_role);
+    }
+
     QDECREF(options);
     *pbs = bs;
     return 0;
@@ -1814,6 +1834,13 @@ void bdrv_close(BlockDriverState *bs)
     notifier_list_notify(&bs->close_notifiers, bs);
 
     if (bs->drv) {
+        BdrvChild *child, *next;
+
+        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
+            QLIST_REMOVE(child, next);
+            g_free(child);
+        }
+
         if (bs->backing_hd) {
             BlockDriverState *backing_hd = bs->backing_hd;
             bdrv_set_backing_hd(bs, NULL);
@@ -2005,9 +2032,18 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
         QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs_old, node_list);
     }
 
+    /*
+     * Update lh_first.le_prev for non-empty lists.
+     *
+     * The head of the op blocker list doesn't change because it is moved back
+     * in bdrv_move_feature_fields().
+     */
     assert(QLIST_EMPTY(&bs_old->tracked_requests));
     assert(QLIST_EMPTY(&bs_new->tracked_requests));
 
+    QLIST_FIX_HEAD_PTR(&bs_new->children, next);
+    QLIST_FIX_HEAD_PTR(&bs_old->children, next);
+
     bdrv_rebind(bs_new);
     bdrv_rebind(bs_old);
 }
@@ -2030,6 +2066,7 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
     /* The contents of 'tmp' will become bs_top, as we are
      * swapping bs_new and bs_top contents. */
     bdrv_set_backing_hd(bs_top, bs_new);
+    bdrv_attach_child(bs_top, bs_new, &child_backing);
 }
 
 static void bdrv_delete(BlockDriverState *bs)