Re: [Qemu-devel] [PATCH] block: mirror - insure that errp is not NULL

[Markus Armbruster <armbru@redhat.com>]

Jeff Cody <jcody@redhat.com> writes:

> When starting a block job, commit_active_start() relies on whether *errp
> is set by mirror_start_job.  This allows it to determine if the mirror
> job start failed, so that it can clean up any changes to open flags from
> the bdrv_reopen().  If errp is NULL, then it will not be able to
> determine if mirror_start_job failed or not.
>
> Reported-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>  block/mirror.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 2a43334..41bb83c 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -634,6 +634,8 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
>      int64_t length, base_length;
>      int orig_base_flags;
>  
> +    assert(errp != NULL);
> +
>      orig_base_flags = bdrv_get_flags(base);
>  
>      if (bdrv_reopen(base, bs->open_flags, errp)) {

Needed, because:

       mirror_start_job(bs, base, speed, 0, 0,
                        on_error, on_error, cb, opaque, errp,
                        &commit_active_job_driver, false, base);
       if (error_is_set(errp)) {

When your callers may legitimately ignore errors, you have to do
something like

       local_err = NULL;
       mirror_start_job(bs, base, speed, 0, 0,
                        on_error, on_error, cb, opaque, &local_err,
                        &commit_active_job_driver, false, base);
       error_propagate(errp, local_err);
       if (local_err) {

But here, the assertion should do fine.

Reviewed-by: Markus Armbruster <armbru@redhat.com>