[Libguestfs] [PATCH libnbd 4/7] lib: Allow closure user_data to be associated with a free callback.

[Eric Blake]

On 8/12/19 11:08 AM, Richard W.M. Jones wrote:
> Mechanical change: Wherever we call any closure with the
> LIBNBD_CALLBACK_FREE function, we also call nbd_internal_free_callback
> with the closure's user_data.  This allows calls to associate a free
> callback with any closure via its user_data pointer.
> ---

> +++ b/lib/aio.c
> @@ -43,6 +43,10 @@ nbd_internal_retire_and_free_command (struct nbd_handle *h,
>      cmd->cb.completion (LIBNBD_CALLBACK_FREE, cmd->cb.user_data,
>                          NULL);
>  
> +  /* Free the closures if there's an associated free callback. */
> +  nbd_internal_free_callback (h, cmd->cb.fn_user_data);

This calls the fn_user_data callback too many times if it was already
reached.  Instead, you need:

if (cmd->type == NBD_CMD_BLOCK_STATUS && cmd->cb.fn.extent) {
  cmd->cb.fn.extent (_FREE...);
  nbd_internal_free_callback (h, cmd->cb.fn_user_data);
}
else if (cmd->type == NBD_CMD_BLOCK_READ && cmd->cb.fn.chunk) {
  cmd->cb.fn.chunk (_FREE...);
  nbd_internal_free_callback (h, cmd->cb.fn_user_data);
}

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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