[Qemu-block] does blk_commit_all need blk_all_next?

[Paolo Bonzini]

blk_commit_all is in block/block-backend.c only because it uses
blk_all_next.  This is also the only reason why it needs a stub
(stubs/blk-commit-all.c).

The only difference between blk_next and blk_all_next is that the latter
"iterates over all BlockBackends, even the ones which are hidden (i.e.
are not referenced by the monitor)".  Should blk_commit_all really
iterate over BlockBackends such as the NBD server or the block jobs'?

Thanks,

Paolo