Re: [Qemu-devel] [PATCH 10/19] block: Drain recursively with a single BDRV_POLL_WHILE()

[Paolo Bonzini]

On 11/04/2018 18:39, Kevin Wolf wrote:
> +    if (atomic_read(&bs->in_flight)) {
> +        return true;
> +    }
> +
> +    if (recursive) {
> +        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {

QLIST_FOREACH_SAFE is only safe if child disappears, but not if e.g.
next disappears.  So this loop is only safe because top_level is false
below.  Sounds like another good reason to split the top_level == false
case into a separate function.

Paolo

> +            if (bdrv_drain_poll(child->bs, false, recursive)) {
> +                return true;
> +            }
> +        }