[Libguestfs] [PATCH libnbd v2 3/3] api: Add nbd_clear_debug_callback.

[Eric Blake]

On 8/13/19 10:12 AM, Richard W.M. Jones wrote:
> Commit 0904dd113dfa36485623b3c1756dc1aeab3dddeb removed the
> theoretical possibility of clearing the debug callback from the handle
> by setting it to NULL (although that was dubious from an API point of
> view).
> 
> This commit adds an explicit way to do this.  Another advantage of
> this is we can internally call this API from other places when we want
> to clear/free the debug callback.
> ---
>  generator/generator | 11 +++++++++++
>  lib/debug.c         | 17 ++++++++++++++---
>  lib/handle.c        |  4 +---
>  3 files changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/generator/generator b/generator/generator
> index 6ccfc5f..d76eeea 100755
> --- a/generator/generator
> +++ b/generator/generator
> @@ -1013,6 +1013,17 @@ a handle then messages are printed on C<stderr>.
>  
>  The callback should not call C<nbd_*> APIs on the same handle since it can
>  be called while holding the handle lock and will cause a deadlock.";
> +};
> +
> +  "clear_debug_callback", {
> +    default_call with
> +    args = [];
> +    ret = RErr;

Is RErr the right type, or can we make this a 'never fails' function?

> +    shortdesc = "clear the debug callback";
> +    longdesc = "\
> +Remove the debug callback if one was previously associated
> +with the handle (with C<nbd_set_debug_callback>).  If not

s/not/no/

> +callback was associated this does nothing.";
>  };
>  
>    "set_handle_name", {
> diff --git a/lib/debug.c b/lib/debug.c
> index ad4d9cb..c1decb2 100644
> --- a/lib/debug.c
> +++ b/lib/debug.c
> @@ -38,13 +38,24 @@ nbd_unlocked_get_debug (struct nbd_handle *h)
>    return h->debug;
>  }
>  
> +int
> +nbd_unlocked_clear_debug_callback (struct nbd_handle *h)
> +{
> +  if (h->debug_callback)
> +    /* ignore return value */
> +    h->debug_callback (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL);
> +  h->debug_callback = NULL;
> +  h->debug_data = NULL;
> +  return 0;
> +}

Is it worth returning -1 if no callback was associated, and/or
forwarding the return value of callback(FREE, ptr) as the return value
of this function?  (That's more complicated; I'm also fine with always
returning 0 and ignoring the callback(FREE) return).

ACK with the typo fix.

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

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