Re: [PATCH 08/12] reopen: add a transaction to drain_end nodes picked in bdrv_reopen_parse_file_or_backing

[Stefan Hajnoczi]

On Tue, Jan 18, 2022 at 11:27:34AM -0500, Emanuele Giuseppe Esposito wrote:
> Depending on the options given to reopen_state,
> bdrv_reopen_parse_file_or_backing could pick another bs
> that could be from another graph, and thus not protected
> by subtree_drained_begin called by the callers of this
> function.
> 
> We can't simply drain-undrain here, because of transactions.
> To simplify the logic, transactions always assume that they
> are run under drain, so the various subtree_drain introduced
> so far always take care of covering tran_commit().
> 
> And since we cannot directly do it, as the transaction is
> created/committed higher above, we can just add a new
> transaction to the list that just executes subtree_drained_end
> to match the drained_begin done in this function.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
>  block.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/block.c b/block.c
> index fb5bc3077a..fcc44a49a0 100644
> --- a/block.c
> +++ b/block.c
> @@ -4522,6 +4522,10 @@ int bdrv_reopen_set_read_only(BlockDriverState *bs, 
> bool read_only,
>      return bdrv_reopen(bs, opts, true, errp);
>  }
>  
> +TransactionActionDrv bdrv_drv_subtree_end = {
> +    .clean = (void (*)(void *)) bdrv_subtree_drained_end_unlocked,

Please don't cast function pointers. If the types don't match please
define a wrapper function so the compiler can check the types.

signature.asc
Description: PGP signature