On Thu, Apr 18, 2013 at 10:06:06AM +0300, Michael S. Tsirkin wrote:
> On Thu, Apr 18, 2013 at 09:05:52AM +0800, Asias He wrote:
> > This helper is useful to check if a feature is supported.
> >
> > Signed-off-by: Asias He <asias@xxxxxxxxxx>
> > Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
>
> Why do we need the locking here by the way?
> It seems features don't change while vhost
> is running.
See:
static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
{
unsigned acked_features;
/* TODO: check that we are running from vhost_worker or dev mutex is
* held? */
acked_features = rcu_dereference_index_check(dev->acked_features, 1);
return acked_features & (1 << bit);
}
We are accessing it outside the vhost_worker thread.
> > ---
> > drivers/vhost/tcm_vhost.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> > index 957a0b9..88ebb79 100644
> > --- a/drivers/vhost/tcm_vhost.c
> > +++ b/drivers/vhost/tcm_vhost.c
> > @@ -99,6 +99,18 @@ static int iov_num_pages(struct iovec *iov)
> > ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
> > }
> >
> > +static bool tcm_vhost_check_feature(struct vhost_scsi *vs, int feature)
> > +{
> > + bool ret = false;
> > +
> > + mutex_lock(&vs->dev.mutex);
> > + if (vhost_has_feature(&vs->dev, feature))
> > + ret = true;
> > + mutex_unlock(&vs->dev.mutex);
> > +
> > + return ret;
> > +}
> > +
> > static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
> > {
> > return 1;
> > --
> > 1.8.1.4
--
Asias
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