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

[Fam Zheng <famz@redhat.com>]

On Thu, 02/13 07:40, Markus Armbruster wrote:
> 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.

Thanks for the explanation!

Reviewed-by: Fam Zheng <famz@redhat.com>