block: Support inactive nodes in blk_insert_bs()

Device models have a relatively complex way to set up their block
backends, in which blk_attach_dev() sets blk->disable_perm = true.
We want to support inactive images in exports, too, so that
qemu-storage-daemon can be used with migration. Because they don't use
blk_attach_dev(), they need another way to set this flag. The most
convenient is to do this automatically when an inactive node is attached
to a BlockBackend that can be inactivated.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250204211407.381505-10-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index cc6f58a..9288f7e 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -900,14 +900,24 @@ void blk_remove_bs(BlockBackend *blk)
 int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp)
 {
     ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
+    uint64_t perm, shared_perm;
 
     GLOBAL_STATE_CODE();
     bdrv_ref(bs);
     bdrv_graph_wrlock();
+
+    if ((bs->open_flags & BDRV_O_INACTIVE) && blk_can_inactivate(blk)) {
+        blk->disable_perm = true;
+        perm = 0;
+        shared_perm = BLK_PERM_ALL;
+    } else {
+        perm = blk->perm;
+        shared_perm = blk->shared_perm;
+    }
+
     blk->root = bdrv_root_attach_child(bs, "root", &child_root,
                                        BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
-                                       blk->perm, blk->shared_perm,
-                                       blk, errp);
+                                       perm, shared_perm, blk, errp);
     bdrv_graph_wrunlock();
     if (blk->root == NULL) {
         return -EPERM;