block: Remove BlockDriverState.blk

This patch removes the remaining users of bs->blk, which will allow us
to have multiple BBs on top of a single BDS. In the meantime, all checks
that are currently in place to prevent the user from creating such
setups can be switched to bdrv_has_blk() instead of accessing BDS.blk.

Future patches can allow them and e.g. enable users to mirror to a block
device that already has a BlockBackend on it.

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

2 files changed, 2 insertions, 10 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 7f2eeb0559..6928d61de4 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -152,7 +152,6 @@ BlockBackend *blk_new_with_bs(Error **errp)
     bs = bdrv_new_root();
     blk->root = bdrv_root_attach_child(bs, "root", &child_root);
     blk->root->opaque = blk;
-    bs->blk = blk;
     return blk;
 }
 
@@ -422,12 +421,10 @@ static BlockBackend *bdrv_first_blk(BlockDriverState *bs)
     BdrvChild *child;
     QLIST_FOREACH(child, &bs->parents, next_parent) {
         if (child->role == &child_root) {
-            assert(bs->blk);
             return child->opaque;
         }
     }
 
-    assert(!bs->blk);
     return NULL;
 }
 
@@ -495,8 +492,6 @@ BlockBackend *blk_by_public(BlockBackendPublic *public)
  */
 void blk_remove_bs(BlockBackend *blk)
 {
-    assert(blk->root->bs->blk == blk);
-
     notifier_list_notify(&blk->remove_bs_notifiers, blk);
     if (blk->public.throttle_state) {
         throttle_timers_detach_aio_context(&blk->public.throttle_timers);
@@ -504,7 +499,6 @@ void blk_remove_bs(BlockBackend *blk)
 
     blk_update_root_state(blk);
 
-    blk->root->bs->blk = NULL;
     bdrv_root_unref_child(blk->root);
     blk->root = NULL;
 }
@@ -514,11 +508,9 @@ void blk_remove_bs(BlockBackend *blk)
  */
 void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs)
 {
-    assert(!blk->root && !bs->blk);
     bdrv_ref(bs);
     blk->root = bdrv_root_attach_child(bs, "root", &child_root);
     blk->root->opaque = blk;
-    bs->blk = blk;
 
     notifier_list_notify(&blk->insert_bs_notifiers, blk);
     if (blk->public.throttle_state) {
diff --git a/block/mirror.c b/block/mirror.c
index 71d7a4e357..b9986d8218 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -468,7 +468,7 @@ static void mirror_exit(BlockJob *job, void *opaque)
 
         /* This was checked in mirror_start_job(), but meanwhile one of the
          * nodes could have been newly attached to a BlockBackend. */
-        if (to_replace->blk && s->target->blk) {
+        if (bdrv_has_blk(to_replace) && bdrv_has_blk(s->target)) {
             error_report("block job: Can't create node with two BlockBackends");
             data->ret = -EINVAL;
             goto out;
@@ -831,7 +831,7 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
     } else {
         replaced_bs = bs;
     }
-    if (replaced_bs->blk && target->blk) {
+    if (bdrv_has_blk(replaced_bs) && bdrv_has_blk(target)) {
         error_setg(errp, "Can't create node with two BlockBackends");
         return;
     }