Am 01.10.2019 um 17:57 hat Vladimir Sementsov-Ogievskiy geschrieben: > 01.10.2019 17:10, John Snow wrote: > > > > > > On 10/1/19 10:00 AM, Vladimir Sementsov-Ogievskiy wrote: > >>> Otherwise: I have a lot of cloudy ideas on how to solve this, but > >>> ultimately what we want is to be able to find the "addressable" name for > >>> the node the bitmap is attached to, which would be the name of the first > >>> ancestor node that isn't a filter. (OR, the name of the block-backend > >>> above that node.) > >> Not the name of ancestor node, it will break mapping: it must be name of > >> the > >> node itself or name of parent (may be through several filters) > >> block-backend > >> > > > > Ah, you are right of course -- because block-backends are the only > > "nodes" for which we actually descend the graph and add the bitmap to > > its child. > > > > So the real back-resolution mechanism is: > > > > - Find the first non-filter ancestor, A > > - if A is not a block-backend, we must use our node-local name. > > - if A's name is empty, we must use our node-local name. > > - If the name we have chosen is not id_wellformed, we have no > > migration-stable addressable name for this bitmap and the migration must > > fail! > > > > > > For resolving bitmap addresses via QMP (node, name) pairs; the > > resolution method would be this: > > > > - if the node-name N is a block-backend, descend the tree until we find > > the first non-filter node V. > > - if the node-name N is a BlockDriverState, use this node directly. > > > > Looks good for me. > > I also think if on destination we have both block-backend with name N and > block-node with name N and the latter is not (filtered) child of the former, > we should fail migration of at least that bitmap. (Hope, nobody reuse > block-backend names as node-names in practice.. (should we restrict it > explicitly ?))
You can't have a node and a BlockBackend of the same name, they share a single namespace. If you try to do so, you get an error. Kevin
