On Wed, Mar 06, 2013 at 10:06:20AM +0100, Stefan Hajnoczi wrote:
> On Wed, Mar 06, 2013 at 02:16:27PM +0800, Asias He wrote:
> > This helper is useful to check if a feature is supported.
> >
> > Signed-off-by: Asias He <asias@xxxxxxxxxx>
> > ---
> > drivers/vhost/tcm_vhost.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> > index b3e50d7..fdbf986 100644
> > --- a/drivers/vhost/tcm_vhost.c
> > +++ b/drivers/vhost/tcm_vhost.c
> > @@ -91,6 +91,20 @@ 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, u64 feature)
> > +{
> > + u64 acked_features;
> > + bool ret = false;
> > +
> > + mutex_lock(&vs->dev.mutex);
> > + acked_features = vs->dev.acked_features;
> > + if (acked_features & 1ULL << feature)
> > + ret = true;
> > + mutex_unlock(&vs->dev.mutex);
> > +
> > + return ret;
> > +}
>
> This is like vhost_has_feature() except it acquires dev.mutex?
>
> In any case it isn't tcm_vhost-specific and could be in vhost.c.
tcm_vhost_check_feature() is called outside the vhost worker thread. So
the dev.mutex is needed.
Mst, what's your preference here? Add vhost_has_feature_locked() in
vhost.c or I use vhost_has_feature() in tcm_vhost_check_feature().
Thanks.
--
Asias
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