Re: [PATCH v3 02/33] block/nbd: fix how state is cleared on nbd_open() failure paths

[Vladimir Sementsov-Ogievskiy]

21.04.2021 17:00, Roman Kagan wrote:
> On Fri, Apr 16, 2021 at 11:08:40AM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > We have two "return error" paths in nbd_open() after
> > nbd_process_options(). Actually we should call nbd_clear_bdrvstate()
> > on these paths. Interesting that nbd_process_options() calls
> > nbd_clear_bdrvstate() by itself.
> >
> > Let's fix leaks and refactor things to be more obvious:
> >
> > - intialize yank at top of nbd_open()
> > - move yank cleanup to nbd_clear_bdrvstate()
> > - refactor nbd_open() so that all failure paths except for
> >    yank-register goes through nbd_clear_bdrvstate()
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
> > ---
> >   block/nbd.c | 36 ++++++++++++++++++------------------
> >   1 file changed, 18 insertions(+), 18 deletions(-)
> >
> > diff --git a/block/nbd.c b/block/nbd.c
> > index 739ae2941f..a407a3814b 100644
> > --- a/block/nbd.c
> > +++ b/block/nbd.c
> > @@ -152,8 +152,12 @@ static void 
> > nbd_co_establish_connection_cancel(BlockDriverState *bs,
> >   static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
> >   static void nbd_yank(void *opaque);
> >   
> > -static void nbd_clear_bdrvstate(BDRVNBDState *s)
> > +static void nbd_clear_bdrvstate(BlockDriverState *bs)
> >   {
> > +    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
> > +
> > +    yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
> > +
> >       object_unref(OBJECT(s->tlscreds));
> >       qapi_free_SocketAddress(s->saddr);
> >       s->saddr = NULL;
> > @@ -2279,9 +2283,6 @@ static int nbd_process_options(BlockDriverState *bs, 
> > QDict *options,
> >       ret = 0;
> >   
> >    error:
> > -    if (ret < 0) {
> > -        nbd_clear_bdrvstate(s);
> > -    }
> >       qemu_opts_del(opts);
> >       return ret;
> >   }
> > @@ -2292,11 +2293,6 @@ static int nbd_open(BlockDriverState *bs, QDict 
> > *options, int flags,
> >       int ret;
> >       BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
> >   
> > -    ret = nbd_process_options(bs, options, errp);
> > -    if (ret < 0) {
> > -        return ret;
> > -    }
> > -
> >       s->bs = bs;
> >       qemu_co_mutex_init(&s->send_mutex);
> >       qemu_co_queue_init(&s->free_sema);
> > @@ -2305,20 +2301,23 @@ static int nbd_open(BlockDriverState *bs, QDict 
> > *options, int flags,
> >           return -EEXIST;
> >       }
> >   
> > +    ret = nbd_process_options(bs, options, errp);
> > +    if (ret < 0) {
> > +        goto fail;
> > +    }
> > +
> >       /*
> >        * establish TCP connection, return error if it fails
> >        * TODO: Configurable retry-until-timeout behaviour.
> >        */
> >       if (nbd_establish_connection(bs, s->saddr, errp) < 0) {
> > -        yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
> > -        return -ECONNREFUSED;
> > +        ret = -ECONNREFUSED;
> > +        goto fail;
> >       }
> >   
> >       ret = nbd_client_handshake(bs, errp);
> Not that this was introduced by this patch, but once you're at it:
> AFAICT nbd_client_handshake() calls yank_unregister_instance() on some
> error path(s); I assume this needs to go too, otherwise it's called
> twice (and asserts).
>
> Roman.

No, nbd_client_handshake() only calls yank_unregister_function(), not instance.

--
Best regards,
Vladimir