On Thu 21 Feb 2019 04:26:39 PM CET, Andrey Shinkevich wrote:
> The block-stream job needs to own the base node as the limiter
> of the copy-on-read operation. So, the base node is included in
> the job node list (block_job_add_bdrv).
> Also, the block-stream job would not allow the base node to go
> away due to the graph modification, e.g. when a filter node is
> inserted between the bottom node and the base node.
> For that reason, the flag BLK_PERM_GRAPH_MOD is unset in the
> shared permission bit mask of the base node.
>
> Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
> ---
> block/stream.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/block/stream.c b/block/stream.c
> index 7a49ac0..c8f93d4 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -259,6 +259,15 @@ void stream_start(const char *job_id, BlockDriverState
> *bs,
> &error_abort);
> }
>
> + if (base) {
> + /*
> + * The base node should not disappear during the job.
> + */
> + block_job_add_bdrv(&s->common, "base", base, 0,
> + BLK_PERM_ALL & ~BLK_PERM_GRAPH_MOD,
> + &error_abort);
I'm not sure if I understand the ~BLK_PERM_GRAPH_MOD bit, what's the
consequence of not removing that permission?
Berto
