| Message ID | 1366247154-3136-2-git-send-email-asias@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@redhat.com> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Why do we need the locking here by the way? It seems features don't change while vhost is running. > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Apr 18, 2013 at 04:25:21PM +0800, Asias He wrote: > 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@redhat.com> > > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > > > > 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. Hmm I see, we allow changing features on the fly, and the reason is the LOG_ALL feature. Okay ... do we ever call this from worker thread? Because if we do, this will deadlock. Maybe add a comment about this. > > > --- > > > 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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@redhat.com> > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > > 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
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;