Re: [PATCH 09/21] block: Mark bdrv_replace_child_tran() GRAPH_WRLOCK

[Emanuele Giuseppe Esposito]

Am 17/08/2023 um 14:50 schrieb Kevin Wolf:
> Instead of taking the writer lock internally, require callers to already
> hold it when calling bdrv_replace_child_tran(). These callers will
> typically already hold the graph lock once the locking work is
> completed, which means that they can't call functions that take it
> internally.
> 
> While a graph lock is held, polling is not allowed. Therefore draining
> the necessary nodes can no longer be done in bdrv_remove_child() and
> bdrv_replace_node_noperm(), but the callers must already make sure that
> they are drained.
> 
> Note that the transaction callbacks still take the lock internally, so
> tran_finalize() must be called without the lock held. This is because
> bdrv_append() also calls bdrv_attach_child_noperm(), which currently
> requires to be called unlocked. Once it changes, the transaction
> callbacks can be changed, too.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>