On Thu, Apr 18, 2013 at 10:09:53AM +0300, Michael S. Tsirkin wrote:
> On Thu, Apr 18, 2013 at 09:05:53AM +0800, Asias He wrote:
> > Signed-off-by: Asias He <as...@redhat.com>
> > ---
> > drivers/vhost/tcm_vhost.c | 18 ++++++++++++++++++
> > 1 file changed, 18 insertions(+)
> >
> > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> > index 88ebb79..8f05528 100644
> > --- a/drivers/vhost/tcm_vhost.c
> > +++ b/drivers/vhost/tcm_vhost.c
> > @@ -111,6 +111,24 @@ static bool tcm_vhost_check_feature(struct vhost_scsi
> > *vs, int feature)
> > return ret;
> > }
> >
> > +static bool tcm_vhost_check_endpoint(struct vhost_virtqueue *vq)
> > +{
> > + bool ret = false;
> > +
> > + /*
> > + * We can handle the vq only after the endpoint is setup by calling the
> > + * VHOST_SCSI_SET_ENDPOINT ioctl.
> > + *
> > + * TODO: Check that we are running from vhost_worker which acts
> > + * as read-side critical section for vhost kind of RCU.
> > + * See the comments in struct vhost_virtqueue in drivers/vhost/vhost.h
> > + */
> > + if (rcu_dereference_check(vq->private_data, 1))
> > + ret = true;
> > +
> > + return ret;
> > +}
> > +
>
> You can't use RCU in this way. You need to actually
> derefence. Instead, just move this within vq mutex
> and do rcu_dereference_protected. document that this function
> requires vq mutex.
Any difference with:
vs_tpg = rcu_dereference_check(vq->private_data, 1);
if (vs_tpg)
return ture
else
return false;
Note, tcm_vhost_check_endpoint() is called in multiple places. Having a
helper is more convenient.
> > static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
> > {
> > return 1;
> > --
> > 1.8.1.4
--
Asias
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